Which definition of A do you mean?

  • A n the 1st letter of the Roman alphabet
  • A n the blood group whose red cells carry the A antigen
  • Adenine n (biochemistry) purine base found in DNA and RNA; pairs with thymine in DNA and with uracil in RNA
  • Ampere n the basic unit of electric current adopted under the Systeme International d'Unites
  • Angstrom n a metric unit of length equal to one ten billionth of a meter (or 0.0001 micron); used to specify wavelengths of electromagnetic radiation
  • Deoxyadenosine Monophosphate n one of the four nucleotides used in building DNA; all four nucleotides have a common phosphate group and a sugar (ribose)
  • Vitamin A n any of several fat-soluble vitamins essential for normal vision; prevents night blindness or inflammation or dryness of the eyes