Source : Webster's Revised Unabridged Dictionary (1913)

-s \-s\
   1. [OE. es, AS. as.] The suffix used to form the plural of
      most words; as in roads, elfs, sides, accounts.

   2. [OE. -s, for older -th, AS. -[eth].] The suffix used to
      form the third person singular indicative of English
      verbs; as in falls, tells, sends.

   3. An adverbial suffix; as in towards, needs, always, --
      originally the genitive, possesive, ending. See {-'s}.