- The first letter of the modern English alphabet.
- Any of the speech sounds represented by the letter a.
- The first in a series.
- Something shaped like the letter A.
- A The best or highest in quality or rank: grade A milk.
- Music.
- The sixth tone in the scale of C major or the first tone in the relative minor scale.
- A key or scale in which A is the tonic.
- A written or printed note representing this tone.
- A string, key, or pipe tuned to the pitch of this tone.
- A One of the four major blood groups in the ABO system. Individuals with this blood group have the A antigen on the surface of their red blood cells, and the anti-B antibody in their blood serum.
from A to Z
- Completely; thoroughly.
a2 (ə; ā when stressed)

indef.art.
- Used before nouns and noun phrases that denote a single but unspecified person or thing: a region; a person.
- Used before terms, such as few or many, that denote number, amount, quantity, or degree: only a few of the voters; a bit more rest; a little excited.
- Used before a proper name to denote a type or a member of a class: the wisdom of a Socrates.
- Used before a mass noun to indicate a single type or example: a dry wine.
- The same: birds of a feather.
- Any: not a drop to drink.
[Middle English, variant of an, an. See an1.]
USAGE NOTE In writing, the form a is used before a word beginning with a consonant sound, regardless of its spelling (a frog, a university). The form an is used before a word beginning with a vowel sound (an orange, an hour). • An was once a common variant before words beginning with h in which the first syllable was unstressed; thus 18th-century authors wrote either a historical or an historical but a history, not an history. This usage made sense in that people often did not pronounce the initial h in words such as historical and heroic, but by the late 19th century educated speakers usually pronounced initial h, and the practice of writing an before such words began to die out. Nowadays it survives primarily before the word historical. One may also come across it in the phrases an hysterectomy or an hereditary trait. These usages are acceptable in formal writing.
a3 (ə)

prep.
In every; to each; per: once a month; one dollar a pound.
[Middle English, from Old English an, in. See on.]
a4 (ə)

aux.v. Informal.
Have: He'd a come if he could.
[Middle English, alteration of haven, to have. See have.]



