The first letter of the English and many other alphabets, frequently used as an abbreviation and also in the marks of schedules or papers, as schedule A, B, C,. Sometimes used in the ancient law books to denote that the paging is the first of that number in the book. As an abbreviation, A is used for anonymous.

Among the Romans this letter was used in criminal trials. The judges were furnished with small tables covered with wax, and each one inscribed on it the initial letter of his vote; A, when he voted to absolve the party on trial; C, when he was for condemnation; and N L, (non liquet) when the matter was unclear and he desired a new argument.