A (
http://definr.com/A)
n 1: the blood group whose red cells carry the A antigen [syn:
A,
type A,
group A]
2: a metric unit of length equal to one ten billionth of a
meter (or 0.0001 micron); used to specify wavelengths of
electromagnetic radiation [syn:
angstrom,
angstrom unit,
A]
3: any of several fat-soluble vitamins essential for normal
vision; prevents night blindness or inflammation or
dryness of the eyes [syn:
vitamin A, {antiophthalmic
factor},
axerophthol,
A]
4: the basic unit of electric current adopted under the System
International d'Unites; "a typical household circuit
carries 15 to 50 amps" [syn:
ampere,
amp,
A]
5: the 1st letter of the Roman alphabet [syn:
A]