Modus \Mo"dus\, n.; pl. Modi. [L. See Mode.] (Old Law)
   1. The arrangement of, or mode of expressing, the terms of a
      contract or conveyance.
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   2. (Law) A qualification involving the idea of variation or
      departure from some general rule or form, in the way of
      either restriction or enlargement, according to the
      circumstances of the case, as in the will of a donor, an
      agreement between parties, and the like. --Bracton.
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   3. (Law) A fixed compensation or equivalent given instead of
      payment of tithes in kind, expressed in full by the phrase
      modus decimandi. --Blackstone.
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            They, from time immemorial, had paid a modus, or
            composition.                          --Landor.
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MODUS, civil law. Manlier; means; way. 

MODUS, eccl. law. Where there is by custom a particular manner of tithing 
allowed, different from the general law of taking tithes in kind, as a 
pecuniary compensation, or the performance of labor, or when any means are 
adopted by which the general law of tithing is altered, and a new method of 
taking them is introduced, it is called a modus decimandi, or special manner 
of taking tithes. 2 Bl. Com. 29.