WordNet sense 1 (any of several fat-soluble vitamins essential for normal vision; prevents night blindness or inflammation or dryness of the eyes):

axerophthol, antiophthalmic factor, vitamin A

WordNet sense 2 (one of the four nucleotides used in building DNA; all four nucleotides have a common phosphate group and a sugar (ribose)):

deoxyadenosine monophosphate

WordNet sense 3 ((biochemistry) purine base found in DNA and RNA; pairs with thymine in DNA and with uracil in RNA):

adenine

WordNet sense 4 (a metric unit of length equal to one ten billionth of a meter (or 0.0001 micron); used to specify wavelengths of electromagnetic radiation):

angstrom, angstrom unit

WordNet sense 5 (the basic unit of electric current adopted under the Systeme International d'Unites):

amp, Ampere

WordNet sense 6 (the 1st letter of the Roman alphabet):

letter a

WordNet sense 7 (the blood group whose red cells carry the A antigen):

group A, type A