The following table is collections of terms from model railroading, railroading, software and hardware.

AAR  RR   Association of American Railroads, the trade association that represents the common interests of the railroad industry in such areas as standards, public relations, and advertising.
AC HW See Alternating Current.
ACC  MR  See CA.
Access hatch  MR  A hole in the benchwork and scenery, sometimes concealed with a lift out section of scenery, for emergency access to parts of the layout.
Accessory decoder  MR  Decoder that provides power and operational control of one or more layout accessory devices, such as turnouts, signals, cranes, animation devices, lighting, etc. Also known as a stationary decoder.
ACI  RR  Automatic Car Identification; see Kar Trak.
Address  MR  In DCC it is used by the command station to communicate with a specific decoder. It can be either 2- or 4-digit, depending on the system, and is typically part of the locomotive’s road number. Addresses are unique to each decoder.
Airbrush  MR  A miniature paint sprayer that gives a controlled application of thinned paint.
All in one track  MR  Model track that includes simulated roadbed or ballast. Also called combination or "click" track.
Alternating Current (AC)  HW  An electric current that reverses its direction of flow at regular intervals. Each move from zero to maximum strength and back to zero is half a cycle. A full cycle includes excursions in both the positive and negative direction.
Ammeter  HW  is a measuring instrument used to measure the electric current in a circuit. Electric currents are measured in amperes (A), hence the name. Instruments used to measure smaller currents, in the milliampere or microampere range, are designated as milliammeters or microammeters. for example, how many amps a locomotive draws when it stalls.
Ampere or amp  HW  is a measure of the amount of electric charge passing a point in an electric circuit per unit time, commonly refered to as current or “i” in Ohm’s law
Application Container  SW  a construct designed to package and run an application or its’ components running on a shared Operating system.[NIST SP 800-180]
AREA  RR  The American Railway Engineering Association is the prototype railroad organization which establishes right of-way material specifications and track construction standards.
Articulated  RR  A steam locomotive with two engines (i.e., cylinders, rods, and wheels) under one boiler.
Automatic reversing  MR  A circuit that senses short circuits and reverses the polarity. Used commonly with reversing loops, wyes, and turntables.
Backdrop  MR  A painting or scenic photograph on the wall behind the layout. It can be as simple as a cloudless sky or it can echo the scenery of the layout and create an illusion of great distance.
Bad order  RR  Defective, out of order.
Ballast  RR  On real railroads, a layer of material – usually crushed rock, cinders, or gravel – on top of the roadbed that holds the ties in position and facilitates drainage. On a model railroad, ballast is simulated by fine gravel spread between the ties and alongside the track.
Balloon track  RR  See Return loop.
Benchwork  mR  Supporting framework for a model railroad layout. L girder and open grid (sometimes called butt joint) are two popular types.
Big hook  RR  Wrecking crane.
Block  RR  On a real railroad, a section of track defined for the purpose of controlling trains. On a model railroad, a block is an electrically isolated section of track.
Block signal  RR  A signal at the entrance to a block (See Block) indicating whether the block is occupied by a train.
Bolster  RR  The crosswise member of the frame of a car at the truck (body bolster) or the crosswise piece at the center of a truck (truck bolster).
Boomer  RR  An experienced railroad man who moves from railroad to railroad.
Booster  mR  In DCC, the booster takes the low-current signal from the command station and "boosts" it to the high-current signal needed by locomotives to operate DC motors, etc., in conformance with NMRA Standards S-91. Also referred to as power stations or power boosters.
Branch line  RR  Secondary line of a railroad.
Brass (also brass hat, brass collar)  RR  Railroad executives and officials.
Bridge  RR  A structure that supports a track passing over a depression in the terrain or a stream. A through bridge has a floor structure, which supports the track between its side beams or trusses, while a deck bridge has its supporting structure below track level.
Bridge guardrail  RR  A set of steel rails mounted inside the running rails on a bridge or other structure to keep derailed cars in line.
Bridge pier  RR  An intermediate support used between bridge spans.
Bridge shoe  RR  An iron or steel casting which transfers the weight of a bridge to its supports. One end is normally a solid mounting while the opposite end allows for expansion and contraction.
Bright Boy  MR  (brand name) An abrasive rubber block used to clean track.
Bumper  RR  A braced, coupler height blocking device that keeps cars from rolling off the end of a track.
Bunk, camp, or outfit car  RR  A passenger or freight car converted into movable living quarters for track workers.
Bus, or bus wire  HW  A main wire, or trunk wire, running under a model railroad. Shorter branch wires, such as track power feeders, are connected to it.
CA  MR  Short for cyanoacrylate adhesive, also known as super glue. A high strength adhesive that can be used on metal and styrene plastic. Sometimes seen as ACC for alphacyanoacrylate cement.
Cab  MR  Usually a handheld piece of equipment with necessary controls to send speed, direction, and other information to the locomotive. Frequently referred to as "throttle". On the prototype, the part of the locomotive that houses the crew.
Cab bus  MR  Used to connect handheld and stationary cabs to a command station. Wireless cabs are indirectly connected to a cab bus via their companion wireless base.
Cab control  MR  A method of independent control of two or more trains in which the throttle for each train is connected to the sections of track or "blocks" in which that train will run. A block is an electrically insulated section of track. Only one engine or set of engines can be independently controlled in each block.
Cab forward  RR  An articulated steam locomotive peculiar to the Southern Pacific, built with the cab in front for visibility in tunnels and snowsheds.
Cab unit  RR  A diesel locomotive built with a full width body. Sometimes called a "covered wagon".
Caboose  RR  The car that carries the crew of a freight train. It is almost always at the rear of the train. Slang terms for the caboose include buggy, bouncer, bobber, cabin, cage, crummy, hack, palace, and way car.
Camelback  RR  A type of steam locomotive with the cab astride the boiler. The Camelback was a solution to the problem of forward visibility past the wide firebox required for burning anthracite.
Can motor  HW  A round-cross section motor with a circular field magnet.
Catenary  RR  A structure built above railroad tracks to carry overhead wire for electric locomotives.
Circuit  HW  The path of an electrical current.
Circuit breaker  HW  A switch that automatically protects the Digital Command Control system and all the decoders on the layout in the event of a current overload.
Class I railroad  RR  The seven major U.S. railroads with average operating revenues in excess of $250 million or more are known as Class I; railroads with revenue of between $20 and $250 million are Class II; less than $20 million earns a Class III rating.
Classification lights  RR  Lights on the front of the locomotive that indicate the type of train. White lights show that the train is an extra; green indicates that another section of the train is following.
Clear board  RR  Green or proceed signal.
Clearance  RR  The space that is required for rolling stock to pass an object or other equipment. Vertical clearance is the space between a car roof and an overhead object or structure.
Clearance point  RR  The location near a turnout frog where equipment on one track may safely pass equipment on the adjacent track.
Click track  MR  See All-in-one track.
Climax  RR  A type of geared steam locomotive used primarily by logging railroads. The two cylinders drive a jackshaft parallel with the axles. Power is transmitted to each truck through bevel gears and a driveshaft; rods couple the axles on each truck. See also Shay and Heisler.
Closure rails  RR  The rails connecting the points and the frog of a turnout.
Coaling station  RR  A structure for storing coal and transferring it into locomotive tenders.
Code  MR  Height of model rail as measured by thousandths of an inch. Code 83 is .083" tall, code 70 is .070", and code 55 is .055".
Combination track  MR  See All in one track.
Command control  MR  A way of controlling model trains by sending electronic signals through the rails or by wireless link, either radio or infrared. Each locomotive has a decoder or receiver that responds only to the messages specifically directed to it. Engines can be controlled independently anywhere on a layout.
Command station  MR  The "brains" of the DCC system. It receives information from the cab, forms the appropriate DCC "packet" and transmits this information in an NMRA DCC-compliant signal to the track via the booster.
Common rail wiring  MR  A wiring system wherein one rail is electrically continuous. A single wire connected to it serves as a common return for two or more cabs.
Configuration variable (CV)  MR  In DCC, number programmed into a decoder that controls its behavior. These numbers remain stored until they are reprogrammed. An address is an example of a configuration variable.
Consist (pronounced CON-sist)  RR  Cars which make up a train; also a list of those cars. A locomotive consist is a group of diesel units put together to pull a train. Also known as "m.u.-ing" (from multiple units). In DCC, with basic consisting, the command station sends the same commands to each loco in the consist. With advanced consisting, each decoder-equipped locomotive responds to the address of the consist, enabling the command station to control the consist with a single command.
Consist address  MR  In DCC, the address to which all digital decoders in a consist respond.
Continuous rail (also welded rail, ribbon rail)  RR  On the prototype, rails that have been welded together to form a single rail hundreds of feet long, eliminating most rail joints, which are the weakest part of the track.
Control bus  HW  A cable connecting the command station to its boosters.
Cookie cutter  MR  A type of table construction in which the plywood tabletop is cut alongside the track and then elevated above the level of the rest of the layout (or dropped below).
Coupler  RR  The device that fastens cars and locomotives together.
Covered wagon  RR  A diesel cab unit, A or B, as opposed to a hood unit.
Cowl unit  RR  A diesel unit that looks like a cab unit but differs structurally in that the carbody is merely a full-width hood rather than a structural part of the locomotive.
Crossing  RR  A track arrangement that permits two tracks to cross but does not allow trains to move from one track to the other. (Also called a "diamond" from its shape.) A level intersection between two tracks or between a track and a highway.
Crossover  RR  Two turnouts laid frog to-frog to allow trains to move from one track to another parallel track.
CTC  RR  Centralized Traffic Control, remote control of turnouts and signals by a dispatcher or control operator.
Cut  RR  Roadbed dug into the surrounding terrain to maintain a relatively even grade.
Cut and fill  RR  A right of way construction method that removes earth or stone above grade and uses it to fill in gaps below grade.
Cut of cars  RR  A number of cars coupled together. The addition of marker lamps and an engine makes the cut of cars a train.
CV  MR  See Configuration variable.
DC  HW  See Direct Current.
DCC  MR  See Digital Command Control.
DCC Bus  HW  Heavy-gauge copper wire used to distribute the electrical power from the booster around the layout. Each booster has its own set of track bus wires. Accessory decoders may be connected to a track bus. The wire gauge of a track bus must be appropriate to the rating of the associated power station and load.
Deadhead  RR  A car or train, usually passenger, moving empty; a passenger traveling on a pass. Empty freight cars are referred to as empties.
Decal  RR  A type of lettering material for models. The letters and numbers are printed on specially prepared paper and then coated with varnish. The lettering is applied by soaking the decal in water to dissolve the film between the ink and the paper and placing the layer of varnish and ink on the car.
Deck  RR  A bridge floor which may be either ballasted or open (with the track bolted to the supports).
Decoder  HW  In DCC, small circuit board that receives digital packets of information addressed to it by the command station in accordance with NMRA standards. Mobile decoders are mounted inside locomotives and control the motor, lights, and sounds. Accessory decoders are used to control non-locomotive items such as turnout motors, signals, etc.
Derail  RR  (verb) to leave the rails; (noun) safety device placed on the track, usually on a siding, to prevent cars from rolling onto the main line – a minor derailment is preferable to a major collision. It may have a cast steel frog that diverts one wheel up and over the rail to stop a car well short of the clearance point. Some derails consist of a single switch point that is normally left open to stop any moving car clear of the main track.
Digital Command Control  MR  Method of controlling multiple trains and accessories using digital communications packets to send commands.
Direct Current  HW  Electrical current that flows in only one direction. Used for control of most model railroads before command control.
Division  RR  A portion of a railroad considered as an operational and administrative unit.
Double crossover  RR  Adjacent trailing and facing-point crossovers allowing trains to pass from one parallel track to the other in either direction.
Double slip switch  RR  A special condensed track component that combines the functions of two turnouts in a shorter distance.
Doubleheader  RR  A train pulled by two locomotives, each with an engine crew, as opposed to diesel or electric locomotive units operating in multiple as a single locomotive with one crew.
Doubling a hill  RR  Splitting a train and taking it up a steep grade in two parts, one at a time.
DPDT  HW  Double-pole, double-throw. Switch used on model railroads to allow you to change the polarity of the current for reverse loops or for complex block control. Some DPDT switches have a "center-off" feature.
Draft gear  RR  The mechanism which connects the coupler to the frame of the car. In the model world, the coupler mounting box is sometimes called the draft gear.
Drawbar  RR  Any coupling, either a solid bar or couplers, between two pieces of rolling stock.
Drawbridge  RR  A movable bridge that spans a navigable waterway.
Dry transfer  MR  Transferable lettering or images on waxy clear film. The lettering material is made of thin plastic with pressure sensitive adhesive, and the letters or images are released from the waxed carrier sheet when rubbed onto a model.
Drybrushing  MR  A painting and weathering technique in which most of the pigment or paint is removed from the brush before the brush is touched to the model. The dry "dry brush" is then stroked lightly over the model to bring out raised details and textures.
Duckunder  MR  A passage underneath layout benchwork requiring ducking or crawling to reach another part of the layout.
Electrostatic grass  MR  Flock that simulates grass. A charge of static electricity makes the fibers stand upright.
Elevated  RR  A reference to a high-level right of way, often constructed on a fill, to provide clearance underneath for another track or a roadway.
Elevation  RR  The measured height of a specific location above a base line.
Enginehouse  RR  A building in which locomotives are serviced and/or stored.
Epoxy  MR  A two part resin and catalyst adhesive that cures rather than dries. The most useful for model building is the type that sets in 5 minutes, called "5-minute epoxy".
Expansion joint  RR  A special slip joint that includes an open space in the center to allow the rails to expand or contract.
Extra  RR  A train not authorized by a timetable schedule.
Facing point  RR  A track turnout positioned so its points face oncoming traffic.
Feeder  HW  Electrical power wire attached to rail.
Fill  RR  Roadbed built up above the surrounding terrain to maintain a relatively even grade.
Fixed cab  MR  A cab or throttle permanently mounted to one location.
Flange  RR  The part of the wheel that runs below and inside the top of the rail to guide the wheel.
Flangeway  RR  The space between a running or stock rail and a guardrail for wheel flanges.
Flash  MR  A thin web of material on a cast part, the result of mold sections not meeting tightly.
Flexible track  MR  Track in long sections (usually 3 feet or 1 meter) that can be bent to any desired curve. Also called "flextrack".
Flextrack  MR  See Flexible track.
Freelance  MR  Modeling that does not follow a prototype railroad.
Frog  RR  The X shaped rail assembly where rails cross in a turnout or crossing.
Function buttons  MR  Buttons on a throttle that control locomotive accessories such as lighting and sound.
Function mapping  MR  In DCC, changing a decoder’s CVs to determine which function button controls which function output.
Function outputs  HW  Wires on a decoder that power locomotive accessories such as lighting. Function outputs are most commonly used to control sound effects and the front and rear headlamps of a locomotive.
M.U.  RR  Multiple unit, a method of controlling several diesel or electric cars or locomotives from one cab. M.U. cars are electric passenger cars for operation on electrified portions of a steam or diesel railroad, as in a suburban district. Interurbans, subway cars, and RDCs are technically M.U. cars, but the term is usually reserved for steam road electric cars.
Main line  RR  The track serving as the main route for trains. Some heavy-use lines have two or more main tracks.
Maintenance of way equipment  RR  The machinery and rolling stock used to keep track and roadbed in good condition.
Markers  RR  Lamps formerly hung on the rear of the last car of the train to show that the cars are indeed a train and to indicate its status. Later substitutes were used, such as reflector paddles. Now replaced on freight trains by end-of-train (EDT) devices; passenger trains now typically have built-in marker lights.
Matte medium  MR  An artist’s material used as an adhesive for ballast and scenery materials.
Microservice  SW  basic element that results from the architectural decomposition of an application’s components into loosely coupled patterns consisting of self contained services that communicate with each other using a standard communications protocol and a set of well-defined APIs, independent of any vendor, product or technology.[NIST SP 800-180]
Milepost  RR  A trackside sign with a number indicating the distance from an established starting point.
Module  MR  A section of a layout built following a standard pattern or dimensions. Each module can be connected interchangeably with any other module built to the same standards. Ntrak is an organization that has developed standards for N scale modules.
MOW  RR  Maintenance of way, the job of keeping track and roadbed in good condition.
Radius  RR  The size of a curve measured from its center point to the center line of a curved track.
Rail  RR  A specialty shaped rolled steel beam with a wide base that’s fastened to crossties to guide trains along the right of way and carry their weight.
Rail code  MR  The height of model rail in thousandths of an inch: code 100 measures .100" tall, code 83 is .083" tall, code 70 is .070", and code 55 is .055".
Rail Diesel Car (RDC)  RR  A self propelled passenger car built by the Budd Company.
Rail joiner  MR  A formed sheet-metal mechanical connector used to join model rails end to end.
Rail nipper  MR  Flush-cutting pliers used to make clean, square cuts in soft metal rail.
Railfan  MR  A person who enjoys riding, watching, photographing, and reading about trains.
Railhead  RR  The wider, top portion of a rail that the wheels run on.
Rectifier  HW  A device inside a decoder for converting electrical AC current into DC current.
Red board  RR  A train order signal indicating orders to be delivered.
Reefer  RR  A refrigerator car. Similar in appearance to a boxcar but has ice or mechanical cooling equipment.
Relay  HW  An electromagnetic switching device commonly used to control polarity, power, and signal circuits.
Rerailer  RR  Section of model track used for getting cars and locomotives back on the rails.
Resistor  HW  Restricts the flow of electrical current to lower its voltage or limit its current.
Return loop  RR  A section of track that reverses the direction of a train running through it; on the prototype more often called a "balloon track".
Reverse loop  RR  See "return loop".
Reverse or "S" curve  RR  Opposing curves connected end to end.
Right-of-way  RR  The track, roadbed, and property along the track owned by the railroad. On a model railroad, the term refers to track, roadbed, and subroadbed.
Rip (repair-in-place) track  RR  The track in a yard where minor car repairs are made.
Riser  MR  A vertical piece in the benchwork that supports a track board or subroadbed.
Road switcher  RR  A general purpose diesel that can be used for both yard switching and road duties. Also called a hood unit.
Roadbed  RR  On real railroads, the foundation layer of earth on which the track is built. On a model railroad, a strip of wood, cork, foam, or other material that simulates the ballast profile of a real railroad.
Rolling stock  RR  comprises all the vehicles that move on a railway. It usually includes both powered and unpowered vehicles, for example locomotives, railroad cars, coaches, and wagons. However, in some countries (including the United Kingdom), the term is usually used to refer only to unpowered vehicles, specifically excluding locomotives which may be referred to as running stock, traction or motive power.
Roundhouse  RR  An enginehouse like a sector of a circle in shape, and usually surrounding a turntable.
RS  RR  American Locomotive Co. (Alco) "road switcher" diesel locomotive.
Ruling grade  RR  The maximum grade that controls train size on a given route.
Runaround  RR  A switching maneuver in which the locomotive uncouples from its train, pulls ahead, backs past on an adjacent track, and moves forward to couple onto the rear of the train; also the track itself where the move takes place.
Running board  RR  Walkway along roof or along sides of tank cars and steam locomotives.