Absorption	When a wave transfers energy to the energy stores of a material
Acceleration	A measure of how quickly velocity is changing
Accurate Result	A result that is very close to the true answer
Activity (radioactive)	The number of nuclei of a sample that decay per second
Air resistance	The frictional force caused by air on a moving object
Alpha decay	A type of radioactive decay in which an alpha particle is given out from a decaying nucleus.
Alpha Particle	A positively-charged particle made up of two protons and two neutrons (a helium nucleus)