1. Elect. ampere; amperes.
2. Physics. angstrom.
4. Brit. arterial (used with a road number to designate a major highway): Take the A525 to Ruthin.
1. the first in order or in a series.
2. ( sometimes l.c. ) (in some grading systems) a grade or mark, as in school or college, indicating the quality of a student's work as excellent or superior.
3. ( sometimes l.c. ) (in some school systems) a symbol designating the first semester of a school year.
a. the sixth tone in the scale of C major or the first tone in the relative minor scale, A minor.
b. a string, key, or pipe tuned to this tone.
c. a written or printed note representing this tone.
d. (in the fixed system of solmization) the sixth tone of the scale of C major, called la.
e. the tonality having A as the tonic note.
5. Physiol. a major blood group, usually enabling a person whose blood is of this type to donate blood to persons of group A or AB and to receive blood from persons of O or A. Cf. ABO system .
6. ( sometimes l.c. ) the medieval Roman numeral for 50 or 500. Cf. Roman numerals .
7. Chem. (formerly) argon.
8. Chem. , Physics. See mass number .
10. Logic. See universal affirmative .
11. Brit. a designation for a motion picture recommended as suitable for adults. Cf. AA (def. 5), U (def. 5), X (def. 9).
12. a proportional shoe width size, narrower than B and wider than AA.
13. a proportional brassiere cup size, smaller than B and larger than AA.
14. a quality rating for a corporate or municipal bond, lower than AA and higher than BBB.