From WordNet (r) 3.0 (2006):
A
n 1: 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]
2: 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]
3: one of the four nucleotides used in building DNA; all four
nucleotides have a common phosphate group and a sugar
(ribose) [syn: deoxyadenosine monophosphate, A]
4: (biochemistry) purine base found in DNA and RNA; pairs with
thymine in DNA and with uracil in RNA [syn: adenine, A]
5: the basic unit of electric current adopted under the Systeme
International d'Unites; "a typical household circuit carries
15 to 50 amps" [syn: ampere, amp, A]
6: the 1st letter of the Roman alphabet [syn: A, a]
7: the blood group whose red cells carry the A antigen [syn:
A, type A, group A]