Source : Webster's Revised Unabridged Dictionary (1913)

Capacity \Ca*pac"i*ty\, n.; pl. {Capacities} (-t[i^]z). [L.
   capacitus, fr. capax, capacis; fr. F. capacit['e]. See
   {Capacious}.]
   1. The power of receiving or containing; extent of room or
      space; passive power; -- used in reference to physical
      things.

            Had our great palace the capacity To camp this host,
            we all would sup together.            --Shak.

            The capacity of the exhausted cylinder. --Boyle.

   2. The power of receiving and holding ideas, knowledge, etc.;
      the comprehensiveness of the mind; the receptive faculty;
      capability of undestanding or feeling.

            Capacity is now properly limited to these [the mere
            passive operations of the mind]; its primary
            signification, which is literally room for, as well
            as its employment, favars this; although it can not
            be dented that there are examples of its usage in an
            active sense.                         --Sir W.
                                                  Hamilton.

   3. Ability; power pertaining to, or resulting from, the
      possession of strength, wealth, or talent; possibility of
      being or of doing.

            The capacity of blessing the people.  --Alex.
                                                  Hamilton.

            A cause with such capacities endued.  --Blackmore.

   4. Outward condition or circumstances; occupation;
      profession; character; position; as, to work in the
      capacity of a mason or a carpenter.

   5. (Law) Legal or noral qualification, as of age, residence,
      character, etc., necessary for certain purposes, as for
      holding office, for marrying, for making contracts, will,
      etc.; legal power or right; competency.

   {Capacity for heat}, the power of absorbing heat. Substances
      differ in the amount of heat requisite to raise them a
      given number of thermometric degrees, and this difference
      is the measure of, or depends upon, what is called their
      capacity for heat. See {Specific heat}, under {Heat}.

   Syn: Ability; faculty; talent; capability; skill; efficiency;
        cleverness. See {Ability}.

Source : WordNet®

capacity
     n 1: ability to perform or produce [ant: {incapacity}]
     2: the susceptibility of something to a particular treatment;
        "the capability of a metal to be fused" [syn: {capability}]
     3: the amount that can be contained; "the gas tank has a
        capacity of 12 gallons" [syn: {content}]
     4: the maximum production possible; "the plant is working at 80
        per cent capacity"
     5: a specified function; "he was employed in the capacity of
        director"; "he should be retained in his present capacity
        at a higher salary"
     6: (computer science) the amount of information (in bytes) that
        can be stored on a disk drive; "the capacity of a hard
        disk drive is usually expressed in megabytes"
     7: an electrical phenomenon whereby an electric charge is
        stored [syn: {capacitance}, {electrical capacity}]
     8: the power to learn or retain knowledge; in law, the ability
        to understand the facts and significance of your behavior
        [syn: {mental ability}] [ant: {incapacity}]
     9: tolerance for alcohol; "he had drunk beyond his capacity"

Source : Free On-Line Dictionary of Computing

capacity
     
         The maximum possible {data transfer rate} of
        a communications channel under ideal conditions.  The total
        capacity of a channel may be shared between several
        independent data streams using some kind of {multiplexing}, in
        which case, each stream's data rate may be limited to a fixed
        fraction of the total capacity.
     
        (2001-05-22)