A, a [ey]
noun, plural A's or As, a's or as.
- the first letter of the English alphabet, a vowel.
- any spoken sound represented by the letter A or a, as in bake, hat, father, or small.
- something having the shape of an A.
- a written or printed representation of the letter A or a.
- a device, as a printer's type, for reproducing the letter A or a.
- from A to Z, from beginning to end; thoroughly; completely: He knows the Bible from A to Z.
- not know from A to B, to know nothing; be ignorant.