The Collaborative International Dictionary of English v.0.48:

Unity \U"ni*ty\, n.; pl. Unities. [OE. unite, F. unit['e], L.
   unitas, from unus one. See One, and cf. Unit.]
   1. The state of being one; oneness.
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            Whatever we can consider as one thing suggests to
            the understanding the idea of unity.  --Locks.
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   Note: Unity is affirmed of a simple substance or indivisible
         monad, or of several particles or parts so intimately
         and closely united as to constitute a separate body or
         thing. See the Synonyms under Union.
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   2. Concord; harmony; conjunction; agreement; uniformity; as,
      a unity of proofs; unity of doctrine.
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            Behold, how good and how pleasant it is for brethren
            to dwell together in unity!           --Ps. cxxxiii.
                                                  1.
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   3. (Math.) Any definite quantity, or aggregate of quantities
      or magnitudes taken as one, or for which 1 is made to
      stand in calculation; thus, in a table of natural sines,
      the radius of the circle is regarded as unity.
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   Note: The number 1, when it is not applied to any particular
         thing, is generally called unity.
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   4. (Poetry & Rhet.) In dramatic composition, one of the
      principles by which a uniform tenor of story and propriety
      of representation are preserved; conformity in a
      composition to these; in oratory, discourse, etc., the due
      subordination and reference of every part to the
      development of the leading idea or the eastablishment of
      the main proposition.
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   Note: In the Greek drama, the three unities required were
         those of action, of time, and of place; that is, that
         there should be but one main plot; that the time
         supposed should not exceed twenty-four hours; and that
         the place of the action before the spectators should be
         one and the same throughout the piece.
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   5. (Fine Arts & Mus.) Such a combination of parts as to
      constitute a whole, or a kind of symmetry of style and
      character.
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   6. (Law) The peculiar characteristics of an estate held by
      several in joint tenancy.
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   Note: The properties of it are derived from its unity, which
         is fourfold; unity of interest, unity of title, unity
         of time, and unity of possession; in other words, joint
         tenants have one and the same interest, accruing by one
         and the same conveyance, commencing at the same time,
         and held by one and the same undivided possession.
         Unity of possession is also a joint possession of two
         rights in the same thing by several titles, as when a
         man, having a lease of land, afterward buys the fee
         simple, or, having an easement in the land of another,
         buys the servient estate.
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   At unity, at one.

   Unity of type. (Biol.) See under Type.
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   Syn: Union; oneness; junction; concord; harmony. See Union.
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