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 ]

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 ]

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 ]

(biochemistry) purine base found in DNA and RNA; pairs with thymine in DNA and with uracil in RNA

[ Syn: adenine , a ]

the basic unit of electric current adopted under the Systeme International dUnites; a typical household circuit carries 15 to 50 amps

[ Syn: ampere , amp , a ]

the 1st letter of the Roman alphabet

[ Syn: a , a , a , a ]

the blood group whose red cells carry the A antigen

[ Syn: a , type a , group a ]