\Ton"nage\ (?; 48), n. [From {Ton} a measure.]
1. The weight of goods carried in a boat or a ship.
2. The cubical content or burden of a vessel, or vessels, in
   tons; or, the amount of weight which one or several
   vessels may carry. See {Ton}, n.
   (b) .
             A fleet . . . with an aggregate tonnage of
             60,000 seemed sufficient to conquer the world.
                                               --Motley.
3. A duty or impost on vessels, estimated per ton, or, a
   duty, toll, or rate payable on goods per ton transported
   on canals.
4. The whole amount of shipping estimated by tons; as, the
   tonnage of the United States. See {Ton}.
Note: There are in common use the following terms relating to
      tonnage: (a) Displacement. (b) Register tonnage, gross
      and net. (c) Freight tonnage. (d) Builders'
      measurement. (e) Yacht measurement. The first is mainly
      used for war vessels, where the total weight is likely
      to be nearly constant. The second is the most
      important, being that used for commercial purposes. The
      third and fourth are different rules for ascertaining
      the actual burden-carrying power of a vessel, and the
      fifth is for the proper classification of pleasure
      craft. Gross tonnage expresses the total cubical
      interior of a vessel; net tonnage, the cubical space
      actually available for freight-carrying purposes. Rules
      for ascertaining these measurements are established by
      law.