In English a represents unaccented forms of several words, e.g. an (one), of, have, he, and or various prefixes the history of which is given in detail in the New English Dictionary (Oxford, 1888), vol. i. p. 4. (P. GI.)

As a symbol the letter is used in various connexions and for various technical purposes, e.g. for a note in music, for the first of the seven dominical letters (this use is derived from its being the first of the litterae nundinales at Rome), and generally as a sign of priority.

In Logic, the letter A is used as a symbol for the universal affirmative proposition in the general form ``all x is y.'' The letters I, E and O are used respectively for the particular affirmative ``some x is y,'' the universal negative ``no x is y,'' and the particular negative ``some x is not y.'' The use of these letters is generally derived from the vowels of the two Latin verbs AffIrmo (or AIo), ``I assert,'' and nEgO, ``I deny.'' The use of the symbols dates from the 13th century, though some authorities trace their origin to the Greek logicians. A is also used largely in abbreviations (q.v.).

In Shipping, A1 is a symbol used to dennote quality of construction and material. In the various shipping registers ships are classed and given a rating after an official examination, and assigned a classification mark, which appears in addition to other particulars in those registers after the name of the ship. See SHIPBUILDING. It is popularly used to indicate the highest degree of excellence.

AA, the name of a large number of small European rivers. The word is derived from the Old German aha, cognate to the Latin aqua, water (cf. Ger.-ach; Scand. a, aa, pronounced o). The following are the more important streams of this name:--Two rivers in the west of Russia, both falling into the Gulf of Riga, near Riga, which is situated between them; a river in the north of France, falling into the sea below Gravelines, and navigable as far as St Omer; and a river of Switzerland, in the cantons of Lucerne and Aargau, which carries the waters of Lakes Baldegger and Hallwiler into the Aar. In Germany there are the Westphalian Aa, rising in the Teutoburger Wald, and joining the Werre at Herford, the Munster Aa, a tributary of the Ems, and others.