A

Abbreviation or symbol for absolute temperature, absorption coefficient, acceleration, adenine, ampere, amplitude, angular acceleration, area, attenuation coefficient, fine-structure constant, helium nucleus, Helmhotz free energy, magnetic vector potential, relative atomic mass, a stereoisomer of a sugar, substitution on a carbon atom next to one common to two condensed aromatic nuclei, substitution on the carbon atom next to the hetero-atom in ahetero-cyclic compound, and substitution on the carbon atom of a chain next to the functional group