a

Definitions of a in various dictionaries:

noun - a metric unit of length equal to one ten billionth of a meter (or 0.0001 micron)

noun - any of several fat-soluble vitamins essential for normal vision

noun - one of the four nucleotides used in building DNA

noun - (biochemistry) purine base found in DNA and RNA

noun - the basic unit of electric current adopted under the Systeme International d'Unites

noun - the 1st letter of the Roman alphabet

noun - the blood group whose red cells carry the A antigen

The first letter of the modern English alphabet.

Any of the speech sounds represented by the letter a.

The first in a series.

The best or highest in quality or rank: grade A milk.

Something shaped like the letter A.

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.

Used before noun s 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.

In modern written English, the form a is used before a word beginning with a consonant sound, however it may be spelled (a frog, a university, a euphemism).

In every; to each; per: once a month; one dollar a pound.

Have: He’d a come if he could.

Absent.

Acceleration.

Are (measurement).

A - A (named , plural As, A's, as, a's or aes) is the first letter and the first vowel of the ISO basic Latin alphabet. It is similar to the Ancient Gree...