Noun a has 7 senses
  1. A, type A, group A - the blood group whose red cells carry the A antigen
    --1 is a kind of blood group, blood type
  2. angstrom, angstrom unit, A - a metric unit of length equal to one ten billionth of a meter (or 0.0001 micron); used to specify wavelengths of electromagnetic radiation
    --2 is a kind of metric linear unit
    --2 is a part of
     nanometer, nanometre, nm, millimicron, micromillimeter, micromillimetre
    --2 has parts: picometer, picometre, micromicron
  3. vitamin A, antiophthalmic factor, axerophthol, A - any of several fat-soluble vitamins essential for normal vision; prevents night blindness or inflammation or dryness of the eyes
    --3 is a kind of fat-soluble vitamin
    --3 has particulars: vitamin A1, retinol; vitamin A2, dehydroretinol
  4. deoxyadenosine monophosphate, A - one of the four nucleotides used in building DNA; all four nucleotides have a common phosphate group and a sugar (ribose)
    --4 is a kind of nucleotide
  5. adenine, A - (biochemistry) purine base found in DNA and RNA; pairs with thymine in DNA and with uracil in RNA
    --5 is a kind of purine
    --5 is a substance of
     deoxyribonucleic acid, desoxyribonucleic acid, DNA; ribonucleic acid, RNA
  6. ampere, amp, A - the basic unit of electric current adopted under the Systeme International d'Unites; "a typical household circuit carries 15 to 50 amps"
    --6 is a kind of current unit
    --6 is a part of abampere, abamp
    --6 has parts: milliampere, mA
  7. A - the 1st letter of the Roman alphabet
    --7 is a kind of
    letter, letter of the alphabet, alphabetic character
    --7 is a member of Roman alphabet, Latin alphabet
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