First recorded before 900; Middle English; Old English am, eam, eom; cognate with Gothic im, Old Norse, Armenian em, Old Irish am (from unattested esmi ), Attic Greek eimí, Aeolic Greek émmi, Doric Greek ēmí (all from prehistoric Greek esmi ), Hittite esmi, early Lithuanian esmì, Old Church Slavonic yesmĭ, Albanian jam (from unattested esmi ), Sanskrit ásmi, from unattested Proto-Indo-European ésmi, from root es- “to be” + -m 1st person singular + -i, present-time marker; cf. is
The abbreviation a.m. for Latin ante merīdiem, meaning “before noon,” refers to the period from midnight until noon. One minute before noon is 11:59 a.m. One minute after noon is 12:01 p.m. Many people distinguish between noon and midnight by saying 12 noon and 12 midnight. Expressions combining a.m. with morning ( 6 a.m. in the morning ) and p.m. with afternoon, evening, or night ( 9 p.m. at night ) are redundant and occur most often in casual speech and writing. Both a.m. and p.m. sometimes appear in capital letters, especially in printed matter.