Both in derivation and usage, φονεύς and ἀνθρωποκτόνος are distinguished from each other just as the English murderer from manslayer or homicide. σικάριος, used only in Ac. xxi. 38, is the Latin sicarius, and means an assassin, usually hired for the work, who furtively stabbed his enemy with a short sword, the Latin sica. φονεύς is a generic word and may denote a murderer of any kind, σικάριος being one of the specific varieties which it includes.