On an average

Average \Av"er*age\, n. [OF. average, LL. averagium, prob. fr.
   OF. aver, F. avoir, property, horses, cattle, etc.; prop.
   infin., to have, from L. habere to have. Cf. F. av['e]rage
   small cattle, and avarie (perh. of different origin) damage
   to ship or cargo, port dues. The first meaning was perhaps
   the service of carting a feudal lord's wheat, then charge for
   carriage, the contribution towards loss of things carried, in
   proportion to the amount of each person's property. Cf.
   {Aver}, n., {Avercorn}, {Averpenny}.]
   1. (OLd Eng. Law) That service which a tenant owed his lord,
      to be done by the work beasts of the tenant, as the
      carriage of wheat, turf, etc.
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   2. [Cf. F. avarie damage to ship or cargo.] (Com.)
      (a) A tariff or duty on goods, etc. [Obs.]
      (b) Any charge in addition to the regular charge for
          freight of goods shipped.
      (c) A contribution to a loss or charge which has been
          imposed upon one of several for the general benefit;
          damage done by sea perils.
      (d) The equitable and proportionate distribution of loss
          or expense among all interested.
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   {General average}, a contribution made, by all parties
      concerned in a sea adventure, toward a loss occasioned by
      the voluntary sacrifice of the property of some of the
      parties in interest for the benefit of all. It is called
      general average, because it falls upon the gross amount of
      ship, cargo, and freight at risk and saved by the
      sacrifice. --Kent.

   {Particular average} signifies the damage or partial loss
      happening to the ship, or cargo, or freight, in
      consequence of some fortuitous or unavoidable accident;
      and it is borne by the individual owners of the articles
      damaged, or by their insurers.

   {Petty averages} are sundry small charges, which occur
      regularly, and are necessarily defrayed by the master in
      the usual course of a voyage; such as port charges, common
      pilotage, and the like, which formerly were, and in some
      cases still are, borne partly by the ship and partly by
      the cargo. In the clause commonly found in bills of
      lading, "primage and average accustomed," average means a
      kind of composition established by usage for such charges,
      which were formerly assessed by way of average. --Arnould.
      --Abbott. --Phillips.
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   3. A mean proportion, medial sum or quantity, made out of
      unequal sums or quantities; an arithmetical mean. Thus, if
      A loses 5 dollars, B 9, and C 16, the sum is 30, and the
      average 10.
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   4. Any medial estimate or general statement derived from a
      comparison of diverse specific cases; a medium or usual
      size, quantity, quality, rate, etc. "The average of
      sensations." --Paley.
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   5. pl. In the English corn trade, the medial price of the
      several kinds of grain in the principal corn markets.
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   {On an average}, taking the mean of unequal numbers or
      quantities.
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