Definition of A in English:


(also a)


  • 1The first letter of the alphabet.

    1. 1.1Denoting the first in a set of items, categories, sizes, etc.
    2. 1.2Denoting the first of two or more hypothetical people or things.
      ‘suppose A had killed B’
    3. 1.3The highest class of academic mark.
    4. 1.4Chess Denoting the first file from the left, as viewed from white's side of the board.
    5. 1.5The first fixed quantity in an algebraic expression.
    6. 1.6The human blood type (in the ABO system) containing the A agglutinogen and lacking the B.
  • 2A shape like that of a capital A.

    [in combination] ‘an A-shape’
    See also a-frame, A-line
  • 3Music
    The sixth note of the diatonic scale of C major.

    1. 3.1A key based on a scale with A as its keynote.