Glossary

This page provides a glossary of terms.

Summary

The Restart Wiki tries to assume no previous knowledge, only a willingness to learn, and so we try to introduce and explain technical terms as we go along. But you might dip in and out or read the end of an article before the beginning. So this page gathers together as many technical terms as possible, cross-referenced and linked in to main wiki articles where relevant.

If you prefer, you can also use your favourite search engine or Wikipedia to look up unfamiliar terms - these will often give you more detail.

Glossary of Terms

0-9 A B C D E F G H I J K L M N O P Q R S T U V W XYZ

Term	Meaning
0 - 9
2FA	See Two factor Authentication.
A
AC	Alternating Current. An electrical supply which reverses direction many times per second. See AC and DC in the Wiki.
AC/DC motor	A type of electric motor that runs equally well on AC or DC. See DC and Universal (AC/DC) Motors in the wiki.
Adware	A type of malware which presents you with unwanted advertising that you never knowingly agreed to receive.
AF	Audio Frequency. A frequency within the audible range of approximately 20Hz - 20kHz.
Aftermarket	Spare parts, consumables or accessories for an item not manufactured and sold by the item's manufacturer, but by a third party.
AM	Amplitude Modulation. A method of modulation in which the amplitude of an RF signal is modulated by the AF signal to be transmitted. See Amplitude Modulation in the Wiki.
Amp (A)	The unit of electric current, i.e. the quantity of electricity passing, a bit like the amount of water flowing in a river. See Electric circuits, volts amps watts and ohms in the Wiki.
Anode	A positive electrode.
B
BC	Bayonet Cap. A type of lamp base fitted with a push-and-twist action. There are several sizes but the 22mm diameter size is much the commonest. See Types of bulb in the Wiki.
Binary	A number system using only the digits 0 and 1, well suited to computers as they can represent those digits by the on and off states of a switch.
BIOS	Basic Input/Output System. A program built in to PCs up until around 2011, which controls the PC prior to booting and initiates the boot process. (Newer computers use UEFI). See BIOS vs UEFI in the Wiki.
Bipolar Transistor	Another name for a junction transistor.
Bit	A binary digit, representing one of two values or states, such as 1/0, or yes/no, or love/hate Marmite.
Bluetooth	A personal area networking protocol allowing an individual's personal devices to communicate with one another.
Bot	Short for Robot. A computer which has been compromised in order to use its Internet connection for spreading spam or malware. Usually it will be one of many such computers comprising a "botnet", under the control of a "bot herder".
Brick	To "brick" a device is to render it completely useless, i.e. as much use as a brick.
Bridge Rectifier	Four diodes connected in a square. Applying AC to two opposite corners, you get DC out of the other two. See Linear Power Supplies in the Wiki.
Brush	A small block of graphite, a pair of which feed the current to the rotor of an AC/DC motor via the commutator. See DC and Universal (AC/DC) Motors in the Wiki.
Brushless Motor	A type of DC motor which uses an electronic circuit to switch the current between several coils in order to keep the motor turning, instead of using a commutator and brushes to perform this function. See DC and Universal (AC/DC) Motors in the Wiki.
Byte	8 bits, which can be used to represent a single letter, number or punctuation mark, or a number between 0 and 255, or anything else that can have up to 256 values.
C
Capacitor	An electronic component which can store electric charge. Its capacitance is measured in Farads. See Capacitors in the Wiki.
Cathode	A negative electrode.
CFL	See Compact Florescent lamp.
Circuit	Electricity really hates piling up, so it will only flow if it can go around a complete circuit and come back to where it started.
Circuit Diagram	A vacuum cleaner, for example, may contain several paths or "circuits" around which the current can flow, and a computer may contain a huge number. A circuit diagram is a picture of all those paths (or some of them) allowing you to understand how it works.
Commutator	Part of the rotor of an AC/DC motor which receives the current from the brushes. See DC and Universal (AC/DC) Motors in the Wiki.
Compact Florescent lamp	A type of light bulb consisting of a florescent tube bent into a compact shape. More efficient than traditional filament lamps but still falling well short of newer LED lamps. See Types of bulb in the Wiki.
Conductor	A material which conducts electricity. Metals and carbon are conductors.
CPU	Central Processing Unit. The "brains" of a computer, which executes a computer program.
CUI	A user interface operated exclusively with a keyboard by typing commands at a prompt or selecting options from a menu, as opposed to a Graphical User Interface.
D
DAB	Digital Audio Broadcasting. The standard used for digital broadcast radio.
DC	Direct Current. An electrical supply which goes in one direction only. See AC and DC in the Wiki.
DDOS	A Denial of Service attack launched via many different computers across the Internet, so increasing its power and making it harder to defend against.
Decimal	The number system we commonly use, based on the digits 0 - 9.
Diac	A 2-terminal electronic component which switches from a non-conducting to a conducting state when a certain voltage is applied, then remains conducting until the current is switched off. Commonly used in conjunction with a triac in dimmer switches.
DIL	Dual In-Line. A type of IC packaging with 2 parallel rows of pins, designed for through-hole assembly.
Diode	A 2 terminal electronic component allowing a current to flow in one direction but not the other. See Diodes and Rectifiers in the Wiki.
Distro	A flavour of Linux comprising a kernel, a desktop manager and a selection of utilities.
Demodulation	The process of recovering an audio or TV signal (for example) from the RF signal received from an aerial.
DLP	Digital Light Processing. A class of data projector using a DMD to produce the image.
DMD	Digital Micromirror Device. An imaging device which contains a tiny electrically operated mirror to control the brightness of each pixel.
DOA	Dead on Arrival. A brand new item which fails to work when first switched on.
DOS	Denial of Service. An attack which renders a service (such as a website) unusable for its proper purposes. See also DDOS.
E
Earth loop	See Ground loop.
Electrode	An electrical conductor making contact with a non-metallic part of a circuit such as a semiconductor or the electrolyte in a battery.
Electrolyte	A conducting liquid containing negative and positive ions, such as the liquid in a battery
Electrolytic Capacitor	A type of capacitor which employs an electro-chemical process to achieve a high level of capacitance. See Capacitors in the Wiki.
Electromagnet	A coil of wire wound around an iron core. A current passing through the coil magnetises the iron for only as long as the current flows. Typically used in electro-mechanical devices such as toasters, where it holds the lever down while the toast is toasting.
Electron	A sub-atomic particle carrying a negative electrical charge. A flow of electrons constitutes an electric current.
Electronically Commutated Motor	See Brushless Motor.
Encryption	The process of transforming a message or data (the "cleartext") into a completely unintelligible form (the "ciphertext"). Only with knowledge of a secret key can the ciphertext be transformed back into the cleartext.
ES	Edison Screw. A screw-fitting lamp base. Several sizes are in common use. See Types of bulb in the Wiki.
ESD	Electrostatic Discharge. Static caused by friction such as shoes on a carpet, and particularly noticeable in conditions of low humidity. Even if not perceptible, it can damage sensitive electronic components.
Ethernet	A family of networking protocols defining several methods by which packets of data can be transmitted across a computer network.
F
Farad	The unit of capacitance. See Capacitors in the Wiki.
Ferrite rod aerial	A type of aerial used for medium and long wave reception and consisting of a rod or block of ferrite (a magnetic but insulating material) with one or more coils of wire wound around it. See How radios work in the wiki.
Field Effect Transistor	A type of transistor where the current flowing between two of its terminals (the source and the drain) is controlled by an electric field created by a voltage on a third terminal (the gate). See Transistors in the Wiki.
Filament lamp	A type of light bulb containing a thin wire which glows white hot when a current is passed through it. See Types of bulb in the Wiki.
Filing System	That part of an operating system which manages a disk and presents it to the users as individual named files, without the users having to be concerned about where on disk their data is actually stored.
Firmware	Software which is built in to the hardware a computer or smart device and is rarely if ever changed.
Flash	A term used for a type of memory that can only be changed by erasing and rewriting a substantial block of cells at a time. Flashing is used as a verb for the process of rewriting or updating such a memory.
Flux	A liquid or paste which helps to remove oxide or other deposits in order to make good solder joints. Only usually needed for challenging soldering jobs such as surface mount as solder normally contains a core of flux.
FM	Frequency Modulation. A method of modulation in which the frequencyof an RF signal is modulated by the AF signal to be transmitted. See Frequency Modulation in the Wiki.
Frequency	The number of complete (positive and negative) cycles of AC which occur per second. Measured in Hertz.
Full wave rectifier	A rectifier which uses both the positive and negative half cycles of the AC input to produce a DC output. Most often this is achieved with a bridge rectifier.
Fuse	A thin piece of low melting point wire designed to melt and so break the circuit if too much current flows due to a fault.
G
GB	Gigabyte: 1000 megabytes, but often used for 1024 megabytes, which is more properly written GiB.
GHz	A billion Hz
GPT	GUID Partition Table. The name given to newer method of organising the contents of a disk. SeeMBR vs GPT disk layout in the wiki.
Ground loop	When two pieces of audio equipment are connected together, each having its own earth connection, some of the small current that should be going from one of the pieces of equipment to its own earth connection instead goes via the connection to the other equipment's earth, causing an objectionable hum in the audio output.
GUI	Graphical User Interface. Pronounced "goo-ey" A user interface operated principally using a graphical display and a mouse or other pointing device, as opposed to a Character User Interface.
GUID	Globally Unique IDentifier. A 128 bit number used for identifying various types of resource in a computer system.
H
Half wave rectifier	A rectifier which uses only the positive (or the negative) half cycles of the AC input to produce a DC output, by using a single diode.
Hall Effect	When a current flows through a conductor and a magnetic field is applied to the conductor at right angles, the current tends to be pushed to one side of the conductor, at right angles to the magnetic field. This is the Hall Effect. Used in a Hall effect device to detect or measure a magnetic field, for example in smartphones to detect the earth's magnetic field to implement a compass.
Halogen lamp	An improved form of filament lamp with longer life and better efficiency, but still far short of compact florescent and LED lamps. See Types of bulb in the Wiki.
Hard Disk	A computer's main long term storage, which is held on rapidly spinning magnetic disk.
Hardware	The physical electronic and electromechanical parts which comprise a computer.
HD	See Hard Disk
Heat Sink	A piece of metal designed to conduct heat away from a component so as to prevent it getting too hot. When soldering, a pair of pliers can be applied to a lead of a sensitive electronic component as a heat sink to prevent the heat of the solder from damaging the component.
Henry	The unit of inductance. See Inductors in the Wiki.
Hertz (Hz)	The measure of frequency.
Hexadecimal	A number system based on only 16 digits which are represented by 0-9 and A - F. This is useful because each hexadecimal digit can represent 4 bits and 2 hexadecimal digits can represent 8 bits or a byte.
Hole	The lack of an electron in a crystal lattice where there should be one. This leaves behind a positive charge. An electron from an adjacent atom can move into the hole causing the hole to move to the adjacent atom. In this way, holes can act like positively charged particles and carry an electric current.
Hum	A constant low frequency sound in the output of audio equipment due (for example) to inadequate smoothing in the power supply and residual ripple in its output, or to the presence of a ground loop.
Hz	See Hertz.
I
IC	Integrated Circuit. A circuit comprising anything from dozens to billions of electronic components, all fabricated on a single silicon chip. See Integrated Circuits in the Wiki.
IF	Intermediate Frequency. A frequency between the RF and AF in a superhet radio at which most of the amplification and selection of the required station occurs.
Induction motor	A type of electric motor, often used in fans, which only runs on AC. See Induction Motors in the Wiki.
Inductor	A coil of wire, very often wound around a magnetic core, providing a kind of momentum to the flow of electricity. Its inductance is measured in Henrys. See Inductors in the Wiki.
Insulator	A material which doesn't conduct electricity, such as plastic, wood, glass and fresh air.
Integrated Circuit	See IC.
Ion	A positively or negatively charged atom.
J
Jack	The type of plug (and its socket) familiar as a headphone plug.
jFET	Junction Field Effect Transistor. A type of field effect transistor where the gate is formed by a semiconductor junction. See Transistors in the Wiki.
Junction Transistor	A type of transistor with 3 semiconductor layers. Also known as a bipolar transistor. See Transistors in the Wiki.
K
kB	Kilobyte: 1024 bytes.
Kernel	The core of an operating system, which concerns itself with managing the hardware resources at the lowest level. It normally has no user interface, this being provided by another program or programs referred to as the shell. Think of a nut. The shell is what you see but the goodness is inside in the kernel.
Keylogger	A type of malware which logs your keystrokes (including passwords, credit card numbers etc.) and sends them back to its creator, or stores them for him/her to collect later.
kHz	1,000 Hz
L
LAN	Local Area Network. A computer network covering a limited area such as a single building, or at most, a campus.
LCD	Liquid Crystal Display. The type of display used in most calculators, phones, tablets and computer monitors, which uses a special liquid which acts on polarised light under an electric field.
LED	Light Emitting Diode.
Linear Regulator	A circuit often in the form of an IC which produces a constant well defined voltage from a variable or poorly defined higher voltage input, simply by absorbing excess and turning it into heat. See Linear Power Supplies in the Wiki.
Linux	A free, open source operating system kernel which, packaged into a distro, you can use as an alternative to Windows or OS/X.
Live Linux	A Linux system on a bootable CD/DVD or memory stick which can be run from that media without affecting the installed operating system on the hard disk.
Load cell	A device for measuring a force and presenting it as an electrical signal. See Digital weighing scales in the wiki.
Loupe	A magnifying glass, generally without a handle.
M
Magnetron	The device which produces the microwaves in a microwave oven.
Malware	Any bad piece of software which attempts to get onto your computer for malicious purposes.
MB	Megabyte: 1000 kilobytes, but often used for 1024 kilobytes, which is more properly written MiB.
MBR	Master Boot Record. The name given to an older method of organising the contents of a disk. SeeMBR vs GPT disk layoutin the wiki.
MHz	A million Hz
Modulation	The process of impressing an audio or TV signal (for example) an RF signal for transmission.
MOSFET	Metal Oxide Field Effect Transistor. A type of field effect transistor where the gate is formed by metal deposited on an extremely thin insulating oxide layer. See Transistors in the Wiki.
MTBF	Mean Time Between Failures. A measure of the reliability of an item, most usually measured in hours.
Multimeter	An electrical test instrument which measures voltage, current, resistance and often several other things. Most usually they have a digital readout but analogue ones with a dial are also available.
N
N-type	Semiconductor material doped with an impurity whose atoms have one too many electrons to match the crystal lattice, which can carry an electric current as negative charges.
NPN	A type of junction transistor comprising a P-type layer sandwiched between two N-type layers.
O
Object Code	Software in a form that can be directly executed by a computer, but is virtually unintelligible to humans, simply comprising binary numbers.
Octal	A number system based on only 8 digits 0 - 7. This is useful because each octal digit can represent 3 bits.
OEM	Original Equipment Manufacturer. A somewhat confising term generally meaning a company which sells another company's manufactured goods under its own branding and with its own warranty. Also used of software, for a licence allowing a computer manufacturer to install the software on systems they build.(In fact, the manufacturer could be you, building a computer from standard parts.)
Ohm (Ω)	A bit like friction, the unit of resistance to flow of electricity. See Electric circuits, volts amps watts and ohms in the Wiki.
Ohm's Law	The amount of current (Amps) flowing in a circuit is the pressure (Volts) divided by the resistance (Ohms), or I = V / R.
Open Circuit	Electricity likes to go all the way round a circuit and back to where it started. When there is a break in the circuit preventing the current from flowing (maybe due to a fault) this is termed an open circuit.
Open Source	Software or hardware the source code or design of which is non-proprietary and made freely available for anyone to inspect or modify for their own purposes.
Operating System	The software which manages the computing, storage and communications resources of a computer, and presents a user interface allowing the user to run and interact with programs as desired.
Opto coupler	An LED and a phototransistor, electrically isolated but in a single packaged. Used for signalling between two circuits which must have no electrical connection between them.
Oscillator	A circuit which produces an AC output at a chosen frequency.
Own	In hacker parlance, to gain full control of a device or computer through subversive means. See also Pwn.
P
P-type	Semiconductor material doped with an impurity whose atoms have one too few electrons to match the crystal lattice. These result in holes which can effectively carry an electric current as positive charges.
PAN	Personal Area Network. A computer network linking a single person's devices, typically covering, at most, a single room.
Partition	A subdivision of a disk. Under the control of the operating system, a disk can be sliced up like a cake into several partitions, each partition being dedicated to a particular purpose. Otherwise, you would have to install another physical disk for each purpose.
Password Manager	A program or app which stores all your passwords in an encrypted vault under a (hopefully) strong master password. This make it possible to use very strong totally random and unguessable passwords, which most password managers will generate for you.
PAT Test	Portable Appliance Test. This is a basic electrical safety test which should be applied to alll mains operated electrical equipment before and after attempting a repair. It comprises a visual inspection and an automated test. See PAT testing in the Wiki.
Peltier	A thermo-electric effect by which a junction between two different conductors or semiconductors warms if a current is passed through it in one direction and cools if it is passed in the opposite direction. The converse of the Seebeck effect. Used for cooling in mini fridges.
Phillips	A type of cross-head screw or screwdriver, similar to but not quite the same as Posidriv.
Phishing	The criminal practice of sending emails or messages through social media inviting the recipient to open a malicious attachment or visit a malicious website.
Phototransistor	A light-sensitive transistor used for sensing light.
Piezo	The property of some materials to develop a voltage across two opposite faces when a physical force is applied, or to stretch or squeeze slightly if a voltage is applied. Pronounced "pie-eezo" by some and "pee-zo" by others. The Oxford Dictionary allows either, but wars have been started over less contentious issues. Used in some microphones and earpieces, quartz crystal frequency standards, and gas lighters.
Pixel	An individual picture element, or coloured (or black and white) dot, thousands or millions of which make up a digital image.
PNP	A type of junction transistor comprising an N-type layer sandwiched between two P-type layers.
Posidriv	A type of cross-head screw or screwdriver, similar to but not quite the same as Phillips.
Potentiometer (or Pot)	A resistor with a slider than can be moved along its length from one end to the other to tap off any required amount of resistance, for example for a volume control. See Potentiometer in the Wiki.
PPE	Personal Protective Equipment. Equipment such as safety glasses, dust and fumes extractors, respirators, ear plugs, protective clothing etc. used for protection against health and safety hazards.
Primary Battery	A single-use battery.
PUP	Potentially Unwanted Program. Any useless but generally (though not necessarily) harmless program, generally installed by the computer vendor, or (knowingly or unknowingly) installed along with downloaded software, the main purpose of which is generally to sell you some other software which you probably don't want.
Pwn	In hacker parlance, to comprehensively "own" a device or computer. The term derives from a mis-typing of "own" in a video game in the 1990's.
Q
Qubit	A quantum bit which can be in two different states simultaneously. We have never seen one of these at a Restart Party, and if we ever do we will probably be undecided about what to do with it.
R
RAM	Random Access Memory. Very fast memory used by a computer as working store for data and programs currently being processed.
Ransomware	Malware which encrypts all your files then demands a ransom in order to recover them for you.
Rectifier	A diode used for converting AC to DC.
Reed switch	A sealed glass tube containing two magnetic contacts forming a switch. The switch can be closed by bringing a magnet near or by energising an electromagnet. Used as the switch in a reed relay or with a magnet attached to a moving part to detect when a cover is closed, a printer paper drawer is fully inserted, or a float in a tank is indicating the tank is full, etc.
Relay	A device consisting of a switch or bank of switches operated by an electromagnet. The switch(es) may be simple switch contacts or a reed switch.
Reservoir Capacitor	A large value capacitor used for smoothing. See power supplies in the wiki.
Resistor	An electronic component which resists the flow of electricity. It's resistance is measured in Ohms. A resistor always generates heat, even if only a tiny amount, and any replacement must be rated in Watts accordingly. See Resistors in the Wiki.
Resistance	See Ohms.
RF	Radio Frequency. A high frequency capable of being transmitted as a radio signal.
Ripple	Residual variation after smoothing in the voltage of a DC power supply at the frequency or twice the frequency of the AC mains input.
ROM	Read-only memory. Fixed memory which rarely needs to be changed, used for the most basic and lowest level functions in a computer.
Rootkit	An especially pernicious type of malware which subverts the operating system in order to expunge all references to itself and associated malware in listings of files and running programs etc., so as to mask its presence and hinder its removal.
S
Schematic	Another name for a Circuit Diagram.
SCR	Silicon Controlled Rectifier. See Thyristor.
Secondary Battery	A rechargeable battery.
Semiconductor	A material such as silicon, germanium or gallium arsenide which can be made to conduct electricity either by negatively charged electrons (N-type) or by positively charged holes (P-type), by adding small amounts of carefully chosen impurities.
Sector	The smallest block of data a disk can read or write. On older disks this was normally 512 bytes but in modern disks and SSDs it is usually 4096 bytes.
Seebeck	A thermo-electric effect by which a voltage is generated by a junction between two different conductors or semiconductors if it is heated or cooled relative to the rest of the circuit. The converse of the Peltier effect. Used by space craft venturing to the outer reaches of the solar system to generate electricity from a radioactive heat source such as a lump of plutonium.
Shell	A program which offers a user interface to lower level parts of an <#Operating System|operating system]] (referred to as the kernel), which lack a user interface. The Mac or Linux command prompt is referred to as the shell, and the Windows Desktop is Windows' shell.
Short circuit	If two wires are touching which shouldn't the electricity may be able to take a short cut, meeting very little resistance and so allowing too much electricity to flow. This is a Bad Thing and can cause things to get hot or even catch fire.
Shottky diode	A type of diode using a metal-semiconductor junction, mainly used in power supplies on account of its ability to operate efficiently at higher frequencies. See switching mode power supplies in the wiki.
SIL	Single In-Line. A type of packaging used for circuit sub-assemblies, resistor networks and some ICs with a single row of pins, designed for through-hole assembly.
S.M.A.R.T	Self-Monitoring, Analysis, and Reporting Technology. A technology built into all modern hard disks and solid state disks by which the device can monitor things like its error rate in order to report back and hopefully give early warning of impending failure.
Smoothing	The process of turning raw rectified AC, which drops to zero twice in every cycle of the AC, into a reasonably constant voltage. See Why is a power supply needed? in the Wiki.
Software	The step-by-step instructions which tell a computer what to do and how to do it.
Solder	A mixture (most often) of tin and copper or tin and lead with a relatively low melting point, making it very convenient for making electrical connections. (Americans call it "sodder", and many electrons have been harmed in discussions as to which is correct. But the Americans are on their own on this one.)
Solenoid	An inductor or electromagnet in cylindrical form.
Solid State Disk	A faster (though more expensive) alternative to a hard disk for a computer's long term storage.
Source Code	Software in a human-readable form as created by a developer. Generally, this cannot be directly be understood or run by a computer, but has translated by a special program called a compiler into object code.
Spam	Any unwanted email. This may simply be an irritation but often it will be a scam or contain malicious attachments or links.
Spear Phishing	A type of phishing attack directed at a specific victim who has probably been researched in order to make the attack seem highly plausible.
Spudger	A tool with a thin plastic or metal blade typically used (for example) for inserting into the crack between two halves of a plastic case in order to pry it open.
Spyware	A type of malware which reports browsing history and other personal information back to its creator without your permission.
SSD	See Solid State Disk.
Superhet	A common design of radio receiver. See Superhet in the Wiki.
Stepper Motor	A type of motor which, instead of turning continuously, turns by a certain fraction of a revolution and stops every time it is given an electrical pulse. Used, for example, for stepping the paper through a printer as it is being printed. See DC and Universal (AC/DC) Motors in the Wiki.
Surface Mount	A method of manufacture in which electronic components are soldered directly onto the surface of a printed circuit board, as opposed to the older through-hole method.
SWG	Standard Wire Guage. A set of wire diameters where each gauge is approximately 10% thinner than the previous, for example 16 gauge is 1/16in in diameter and 50 gauge is a thousanth of an inch. Cross sectional area in square millimeters is becoming a more usual measure. See Standard Wire Gauge in Wikipedia.
Switch-mode Regulator	A circuit which produces a constant well defined voltage from a variable or poorly defined voltage input, by switching the power on and off very rapidly and smoothing the result. See Switching Mode Power Supplies in the Wiki.
Synchronous motor	A type of electric motor which only runs on AC, and which runs at a speed which is locked to the AC supply frequency. See Synchronous Motors in the Wiki.
T
TB	Terabyte: 1000 gigabytes, but often used for 1024 gigabytes, which is more properly written TiB.
Thermal Paste	A paste with a special formulation making it a good conductor of heat, used to improve the transfer of heat from an electronic component to a heat sink.
Thermistor	An electronic component like a resistor but with a resistance which decreases substantially with increasing temperature.
Through-hole	A method of manufacture in which electronic components are attached to a circuit board by passing their leads or pins through holes in the board and soldering them to the board on the other side, as opposed to the more modern surface mount technique which allows much higher component densities.
Thyristor	An electronic component with 3 leads used as a switch. Also known as a Silicon Controlled Rectifier. See Transistors in the Wiki.
Transducer	A device which transforms energy or a measurement from one form to another, e.g. sound to/from electricity (speakers and microphones), or temperature, light, force etc. to an electrical signal.
Transformer	Two (or more) coils of wire wound around a magnetic core, used to step a voltage up or down or provide isolation between two circuits. See Transformers in the Wiki.
Transistor	An electronic component with 3 leads used to amplify a signal or switch a current on or off. See Transistors in the Wiki.
Triac	A type of thyristor which, unlike the standard type, can be used on AC. Commonly used in dimmer switches.
TRIM	A means by which an operating system can tell an SSD about files that have been deleted. This is important for performance reasons related to the way an SSD works. See SSD Migration and Troubleshooting in the wiki.
Trojan	A type of malware which hides inside legitimate software.
Torx	A type of security screw or screwdriver with a 6-pointed star shape.
Two Factor Authentication	A login scheme where you are required to supply not only a password ("something you know") but also prove your possession of a token of some sort ("something you have") or provide a biometric such as a fingerprint ("something you are").
Tuned Circuit	A capacitor and an inductor connected together, which resonate at a particular frequency.
Two Step Authentication	A kind of "poor man's Two factor Authentication" where the second factor is a one time code delivered to you by text message. Whilst considerably better than a password on its own, this is no longer greatly recommended on account of the relative ease by which a determined criminal could get a SIM card registered to your phone number and so get the one time code.
U
UEFI	Unified Extensible Firmware Interface. A program built in to newer PCs (since around 2011) which controls the PC prior to booting and initiates the boot process. (Older computers used BIOS). See BIOS vs UEFI in the Wiki.
Universal motor	A type of electric motor that runs equally well on AC or DC. See DC and Universal (AC/DC) Motors in the Wiki.
V
Virus	A term commonly used for any type of malware, but strictly meaning self-replicating malware.
Volt (V)	The unit of electrical pressure, a bit like water pressure. See Electric circuits, volts amps watts and ohms in the Wiki.
Vulnerability	A flaw in a website or software product by which it can be compromised for malicious purposes, such as spreading malware.
W
WAN	Wide Area Network. A computer network spanning a substantial geographical area
Watts (W)	The unit of power, calculated by multiplying the Volts by the Amps. See Electric circuits, volts amps watts and ohms in the Wiki.
Wavelength	The distance between successive crests of a radio wave as it travels through the air. See Freqvency vs wavelength in the Wiki.
WiFi	A family of wireless local area networking protocols, allowing a number of computers and other devices within a reasonably confined space to talk to each other.
Worm	A type of malware able to spread across a network, or the whole Internet.
X
XP	An obsolete Windows operating system first released in 2001. Extended support ended in 2014 and remaining users are strongly advised to migrate to a supported operating system as security patches are no longer provided.
Y
Yagi	A type of aerial commonly used for terrestrial television reception, and consisting of an array of parallel rods, the array pointing in the direction of the transmitter.
Z
Zener diode	A type of diode which starts conducting in the reverse (normally non-conducting) direction at a well defined voltage.