The Collaborative International Dictionary of English v.0.48:

Vary \Va"ry\, v. t. [imp. & p. p. Varied; p. pr. & vb. n.
   Varying.] [OE. varien, F. varier, L. variare, fr. varius
   various. See Various, and cf. Variate.]
   [1913 Webster]
   1. To change the aspect of; to alter in form, appearance,
      substance, position, or the like; to make different by a
      partial change; to modify; as, to vary the properties,
      proportions, or nature of a thing; to vary a posture or an
      attitude; to vary one's dress or opinions.
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            Shall we vary our device at will,
            Even as new occasion appears?         --Spenser.
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   2. To change to something else; to transmute; to exchange; to
      alternate.
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            Gods, that never change their state,
            Vary oft their love and hate.         --Waller.
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            We are to vary the customs according to the time and
            country where the scene of action lies. --Dryden.
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   3. To make of different kinds; to make different from one
      another; to diversify; to variegate.
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            God hath varied their inclinations.   --Sir T.
                                                  Browne.
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            God hath here
            Varied his bounty so with new delights. --Milton.
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   4. (Mus.) To embellish; to change fancifully; to present
      under new aspects, as of form, key, measure, etc. See
      Variation, 4.
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The Collaborative International Dictionary of English v.0.48:

Vary \Va"ry\, n.
   Alteration; change. [Obs.] --Shak.
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The Collaborative International Dictionary of English v.0.48:

Vary \Va"ry\, v. i.
   1. To alter, or be altered, in any manner; to suffer a
      partial change; to become different; to be modified; as,
      colors vary in different lights.
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            That each from other differs, first confess;
            Next, that he varies from himself no less. --Pope.
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   2. To differ, or be different; to be unlike or diverse; as,
      the laws of France vary from those of England.
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   3. To alter or change in succession; to alternate; as, one
      mathematical quantity varies inversely as another.
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            While fear and anger, with alternate grace,
            Pant in her breast, and vary in her face. --Addison.
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   4. To deviate; to depart; to swerve; -- followed by from; as,
      to vary from the law, or from reason. -- Locke.
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   5. To disagree; to be at variance or in dissension; as, men
      vary in opinion.
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            The rich jewel which we vary for.     --Webster
                                                  (1623).
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WordNet (r) 3.0 (2006):

vary
    v 1: become different in some particular way, without
         permanently losing one's or its former characteristics or
         essence; "her mood changes in accordance with the weather";
         "The supermarket's selection of vegetables varies according
         to the season" [syn: change, alter, vary]
    2: be at variance with; be out of line with [syn: deviate,
       vary, diverge, depart] [ant: conform]
    3: be subject to change in accordance with a variable; "Prices
       vary"; "His moods vary depending on the weather"
    4: make something more diverse and varied; "Vary the menu" [syn:
       vary, variegate, motley]