| A | the 1st letter of the Roman alphabet |
|---|---|
| A | the blood group whose red cells carry the A antigen |
| A | the basic unit of electric current adopted under the System International d'Unites |
| A | a metric unit of length equal to one ten billionth of a meter (or 0.0001 micron) |
| A | one of the four nucleotides used in building DNA |
| A | any of several fat-soluble vitamins essential for normal vision |
| A | battery used to heat the filaments of a vacuum tube |
| A | (U.S.) denoting a quantity consisting of one thousand million items or units |
| A | to a small degree |
| A | being excessive or unreasonable |
| A | singing without instrumental accompaniment |
| A | singing without instrumental accompaniment |