Source : Webster's Revised Unabridged Dictionary (1913)

Since \Since\ (s[i^]ns), adv. [For sins, contr. fr. OE. sithens,
   sithenes, formed by an adverbial ending (cf. {Besides}) from
   OE. sithen, also shortened into sithe, sin, AS.
   si[eth][eth]an, sy[eth][eth]an, seo[eth][eth]an, afterward,
   then, since, after; properly, after that; fr. s[=i][eth]
   after, later, adv. and prep. (originally a comparative adv.,
   akin to OS. s[=i][eth] afterward, since, OHG. s[=i]d, G. seit
   since, Goth. sei[thorn]us late, ni [thorn]anasei[thorn]s no
   longer) + [eth]on instrumental of the demonstrative and
   article. See {That}.]
   1. From a definite past time until now; as, he went a month
      ago, and I have not seen him since. [1913 Webster]

            We since become the slaves to one man's lust. --B.
                                                  Jonson.

   2. In the time past, counting backward from the present;
      before this or now; ago.

            How many ages since has Virgil writ?  --Roscommon.

            About two years since, it so fell out, that he was
            brought to a great lady's house.      --Sir P.
                                                  Sidney.

   3. When or that. [Obs.]

            Do you remember since we lay all night in the
            windmill in St. George's field?       --Shak.

Since \Since\, prep.
   From the time of; in or during the time subsequent to;
   subsequently to; after; -- usually with a past event or time
   for the object.

         The Lord hath blessed thee, since my coming. --Gen.
                                                  xxx. 30.

         I have a model by which he build a nobler poem than any
         extant since the ancients.               --Dryden.

Since \Since\, conj.
   Seeing that; because; considering; -- formerly followed by
   that.

         Since that my penitence comes after all, Imploring
         pardon.                                  --Shak.

         Since truth and constancy are vain, Since neither love,
         nor sense of pain, Nor force of reason, can persuade,
         Then let example be obeyed.              --Granville.

   Syn: Because; for; as; inasmuch as; considering. See
        {Because}.