8/20    Are the time notations "AM" and "PM" acronyms or abbreviations of
        something?  -- yuen
        \_ AM = "ante meridian", PM = "post meridian"--before/after mid-day.
           Look at http://greenwichmeantime.com/info/noon.htm  -John
           \_ Not quite; it's "meridiem" (Latin singular accusative of
              "meridianus", a 3rd decl noun meaning "midday"). Of course,
              "ante" and "post" mean before and after. -alexf
                \_ American Heritage dictionary accepts "antemeridian" as
                   correct, although your etymology is accurate.  And you're
                   a miserable nitpicking pedant, to boot.  -John
                   \_ I was correcting a mostly-correct answer (hence the
                      "quite"). I was not flaming, and I would rather not
                      get flamed either. Also, take a careful look at the
                      definition of "antemeridian" -- this is a (rare) English
                      word meaning "Of or belonging to the forenoon or
                      `morning.'" according to the OED. According to AHD4,
                      it arose from a Latin noun(?) closely related to the
                      phrase referenced above ("antemeridianus"), but is
                      technically not the same thing, and not the common
                      expansion of "a.m.", according to WordNet, OED, and
                      AHD4. -alexf
              \_ Thanks!