The Collaborative International Dictionary of English v.0.48:

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.
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      (b) Conformity to rule; exactness; close correspondence
          with an example, mood, object of imitation, or the
          like.
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                Plows, to go true, depend much on the truth of
                the ironwork.                     --Mortimer.
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      (c) Fidelity; constancy; steadfastness; faithfulness.
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                Alas! they had been friends in youth,
                But whispering tongues can poison truth.
                                                  --Coleridge.
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      (d) The practice of speaking what is true; freedom from
          falsehood; veracity.
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                If this will not suffice, it must appear
                That malice bears down truth.     --Shak.
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   2. That which is true or certain concerning any matter or
      subject, or generally on all subjects; real state of
      things; fact; verity; reality.
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            Speak ye every man the truth to his neighbor.
                                                  --Zech. viii.
                                                  16.
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            I long to know the truth here of at large. --Shak.
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            The truth depends on, or is only arrived at by, a
            legitimate deduction from all the facts which are
            truly material.                       --Coleridge.
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   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.
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            Even so our boasting . . . is found a truth. --2
                                                  Cor. vii. 14.
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   4. Righteousness; true religion.
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            Grace and truth came by Jesus Christ. --John i. 17.
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            Sanctify them through thy truth; thy word is truth.
                                                  --John xvii.
                                                  17.
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   In truth, in reality; in fact.

   Of a truth, in reality; certainly.

   To do truth, to practice what God commands.
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            He that doeth truth cometh to the light. --John iii.
                                                  21.
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WordNet (r) 3.0 (2006):

in truth
    adv 1: 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: in truth, really, truly]