Source : Webster's Revised Unabridged Dictionary (1913)

Truth \Truth\, n.; pl. {Truths}. [OE. treuthe, trouthe, treowpe,
   AS. tre['o]w?. See {True}; cf. {Troth}, {Betroth}.]
   1. The quality or being true; as:
      (a) Conformity to fact or reality; exact accordance with
          that which is, or has been; or shall be.
      (b) Conformity to rule; exactness; close correspondence
          with an example, mood, object of imitation, or the
          like.

                Plows, to go true, depend much on the truth of
                the ironwork.                     --Mortimer.
      (c) Fidelity; constancy; steadfastness; faithfulness.

                Alas! they had been friends in youth, But
                whispering tongues can poison truth.
                                                  --Coleridge.
      (d) The practice of speaking what is true; freedom from
          falsehood; veracity.

                If this will not suffice, it must appear That
                malice bears down truth.          --Shak.

   2. That which is true or certain concerning any matter or
      subject, or generally on all subjects; real state of
      things; fact; verity; reality.

            Speak ye every man the truth to his neighbor.
                                                  --Zech. viii.
                                                  16.

            I long to know the truth here of at large. --Shak.

            The truth depends on, or is only arrived at by, a
            legitimate deduction from all the facts which are
            truly material.                       --Coleridge.

   3. A true thing; a verified fact; a true statement or
      proposition; an established principle, fixed law, or the
      like; as, the great truths of morals.

            Even so our boasting . . . is found a truth. --2
                                                  Cor. vii. 14.

   4. Righteousness; true religion.

            Grace and truth came by Jesus Christ. --John i. 17.

            Sanctify them through thy truth; thy word is truth.
                                                  --John xvii.
                                                  17.

   {In truth}, in reality; in fact.

   {Of a truth}, in reality; certainly.

   {To do truth}, to practice what God commands.

            He that doeth truth cometh to the light. --John iii.
                                                  21.

Source : WordNet®

in truth
     adv : in fact (used as intensifiers or sentence modifiers); "in
           truth, moral decay hastened the decline of the Roman
           Empire"; "really, you shouldn't have done it"; "a truly
           awful book" [syn: {really}, {truly}]