The Collaborative International Dictionary of English v.0.48:

S \S\ ([e^]s),
   the nineteenth letter of the English alphabet, is a
   consonant, and is often called a sibilant, in allusion to its
   hissing sound. It has two principal sounds; one a mere
   hissing, as in sack, this; the other a vocal hissing (the
   same as that of z), as in is, wise. Besides these it
   sometimes has the sounds of sh and zh, as in sure, measure.
   It generally has its hissing sound at the beginning of words,
   but in the middle and at the end of words its sound is
   determined by usage. In a few words it is silent, as in isle,
   d['e]bris. With the letter h it forms the digraph sh. See
   Guide to pronunciation, [sect][sect] 255-261.
   [1913 Webster]

   Note: Both the form and the name of the letter S are derived
         from the Latin, which got the letter through the Greek
         from the Phoenician. The ultimate origin is Egyptian. S
         is etymologically most nearly related to c, z, t, and
         r; as, in ice, OE. is; E. hence, OE. hennes; E. rase,
         raze; erase, razor; that, G. das; E. reason, F. raison,
         L. ratio; E. was, were; chair, chaise (see C, Z, T, and
         R.).
         [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

-s \-s\
   1. [OE. es, AS. as.] The suffix used to form the plural of
      most words; as in roads, elfs, sides, accounts.
      [1913 Webster]

   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.
      [1913 Webster]

   3. An adverbial suffix; as in towards, needs, always, --
      originally the genitive, possesive, ending. See -'s.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

-'s \-'s\ [OE. -es, AS. -es.] The suffix used to form the
   possessive singular of nouns; as, boy's; man's.
   [1913 Webster] 's \'s\
   A contraction for is or (colloquially) for has. "My heart's
   subdued." --Shak.
   [1913 Webster]

WordNet (r) 3.0 (2006):

s
    n 1: 1/60 of a minute; the basic unit of time adopted under the
         Systeme International d'Unites [syn: second, sec, s]
    2: an abundant tasteless odorless multivalent nonmetallic
       element; best known in yellow crystals; occurs in many
       sulphide and sulphate minerals and even in native form
       (especially in volcanic regions) [syn: sulfur, S,
       sulphur, atomic number 16]
    3: the cardinal compass point that is at 180 degrees [syn:
       south, due south, southward, S]
    4: a unit of conductance equal to the reciprocal of an ohm [syn:
       mho, siemens, reciprocal ohm, S]
    5: the 19th letter of the Roman alphabet [syn: S, s]
    6: (thermodynamics) a thermodynamic quantity representing the
       amount of energy in a system that is no longer available for
       doing mechanical work; "entropy increases as matter and
       energy in the universe degrade to an ultimate state of inert
       uniformity" [syn: randomness, entropy, S]

The Free On-line Dictionary of Computing (30 December 2018):

S

    A statistical analysis language from AT&T.

   ["S: An Interactive Environment for Data Analysis and
   Graphics", Richard A. Becker, Wadsworth 1984].

   (1997-01-21)