1º_ 'Ac' is the chemical symbol for actinium. 2º_ 'Ac' is an abbreviation for "antibody" in immunology. 3º_ 'ac' is the symbol for the surface measurement "acre". 4º_ 'AC' is a short form for alternating current, although in Spanish "AC" is also used. See DC ("direct current"), VAC ("alternating current volts"). 5º_ 'AC' is an abbreviation for the enzyme "adenyl cyclase". 6º_ ' . ac' is the internet domain for Ascension Island, which is mainly used by academic sites around the world. 4º_ See also to . C . ( "before Christ") .
