Centesimum Sexagesimum Quintum: July 21, 2009: Nex
Theme for the remainder of the month: Alphabet Soup
nex, necis
Definition: killing, murder, death
But beware! Other 3-letter words beginning with 'n' and ending with 'x' are "nix, nivis" "snow," "nox, noctis" "night," and "nux, nucis" "nut."
And sorry, I don't have time to do etymology or a sentence for these words today.
NB: Bold and underline == macron