Definition of A

  • 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
  • 2. Any of several fat-soluble vitamins essential for normal vision; prevents night blindness or inflammation or dryness of the eyes Noun
  • 3. One of the four nucleotides used in building DNA; all four nucleotides have a common phosphate group and a sugar (ribose) Noun
  • 4. (biochemistry) purine base found in DNA and RNA; pairs with thymine in DNA and with uracil in RNA Noun
  • 5. The basic unit of electric current adopted under the Systeme International d'Unites Noun
  • 6. The 1st letter of the Roman alphabet Noun
  • 7. The blood group whose red cells carry the A antigen Noun

Synonyms for word "a"

Semanticaly linked words with "a"

Hyponims for word "a"