A

noun

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

   noun.quantity

   Synonyms angstrom angstrom unit

   Source: WordNet 3.0

2. any of several fat-soluble vitamins essential for normal vision; prevents night blindness or inflammation or dryness of the eyes

   noun.substance

   Synonyms antiophthalmic factor axerophthol vitamin a

   Source: WordNet 3.0

3. one of the four nucleotides used in building DNA; all four nucleotides have a common phosphate group and a sugar (ribose)

   noun.substance

   Synonyms c deoxyadenosine monophosphate deoxycytidine monophosphate deoxyguanosine monophosphate deoxythymidine monophosphate g t

   Source: WordNet 3.0

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

   noun.substance

   Synonyms adenine

   Source: WordNet 3.0

5. the basic unit of electric current adopted under the Systeme International d'Unites

   noun.quantity

   Examples

   A typical household circuit carries 15 to 50 amps.

   Synonyms amp ampere

   Source: WordNet 3.0

6. the 1st letter of the Roman alphabet

   noun.communication

   Source: WordNet 3.0

7. the blood group whose red cells carry the A antigen

   noun.body

   Synonyms group a type a

   Source: WordNet 3.0