“ In mathematics, A and the other letters of the alphabet are used, e. g., in Euclid, to represent lines, angles, points, etc. In algebra, a and the other first letters of the alphabet are used to express known quantities, and the last letter to express such as are unknown. ”

“ In commerce, for accepted, and is used specially of bills. A as a symbol stands for:
In logic, a universal affirmative. In music, the 6th note of the diatonic scale of C major corresponding to the la of the Italians and the French. ”