ARTF.
The term ARTF  (almost ready to fly) is given to a model that is mostly built and covered, so there is very little assembly required.

ABS
A type of plastic used to make lightweight cowlings and fairings in models

ACT
Anti crash technology, on board sensors monitor the planes attitude in the sky, and partially take control, and recovery of the model if it is entering a crash situation.

ATV
Adjustable Travel Volume is a adjustable function on a radio that can reduce or increase the movement of a servo.

AFT
This is a term given to the rearward part of a model, or, aft center of gravity (balance point)

Antenna
Usually the external wire on the receiver, or the extendable rigid type on the transmitter

After Run Oil
This is used after the days flying more commonly used when storing engines over a long period. It provides added lubrication and displaces un-burnt fuel in the engine, reducing the risk of corrosion.

Aileron Differential
This is were you can set up a different amount of upward movement to downward movement, for example you may need 15mm of upward but only 10mm of downward, to provide better turning ability in some models.

Ailerons
These are found on each wing panel, when an aileron is raised it creates drag that tends to push that side of the wing down, causing the model to roll in that direction. To roll right for example, the right aileron is raised, causing drag, and at the same time the left aileron moves downward generating extra lift on that side of the wing,

Ailevators
If you have independent elevators you can set up a mix from the radio so that the two elevators act as ailerons, so they work in conjunction with the main ailerons.

Airfoil
The cross section (shape) of a wing when viewed from the tip.

Angle of attack
This describes the angle of the wing in forward motion, as it penetrates the air.

Autorotation
This is where a helicopter can land safely without engine power using the inertia built up in the rotating rotor blades, and applying full collective pitch as a brake just before touchdown.

BEC
Battery eliminator circuitry, this allows the internal radio equipment in the plane to be powered from the main drive battery, therefore saving weight and space by not having to carry an additional receiver battery.

Boom
A thin rod like rear fuselage that supports the tail-plane

Ball Link
A type of connection that connects push rods to servo horns and control horns by means of a ball and socket joint.

Backlash
The amount of free play between two meshed gears, in a servo, or drive train.

Binding
Where control surfaces, or pushrods are not working smoothly this is known as binding.

Buddy Box
This is were two transmitters that are compatible are linked by a lead, called a trainer cord, the object of this is dual control, the instructor takes the plane up into the air and then hands control to the student, by holding the trainer button in or holding a switch on the instructors transmitter, control of the model rests with the pupil, when the pupil looses control or becomes disoriented the instructor releases the button or switch and takes control of the model with his transmitter