\Ten"sion\, n. [L. tensio, from tendere, tensum, to
stretch: cf. F. tension. See {Tense}, a.]
1. The act of stretching or straining; the state of being
   stretched or strained to stiffness; the state of being
   bent strained; as, the tension of the muscles, tension of
   the larynx.
2. Fig.: Extreme strain of mind or excitement of feeling;
   intense effort.
3. The degree of stretching to which a wire, cord, piece of
   timber, or the like, is strained by drawing it in the
   direction of its length; strain. --Gwilt.
4. (Mech.) The force by which a part is pulled when forming
   part of any system in equilibrium or in motion; as, the
   tension of a srting supporting a weight equals that
   weight.
5. A device for checking the delivery of the thread in a
   sewing machine, so as to give the stitch the required
   degree of tightness.
6. (Physics) Expansive force; the force with which the
   particles of a body, as a gas, tend to recede from each
   other and occupy a larger space; elastic force;
   elasticity; as, the tension of vapor; the tension of air.
7. (Elec.) The quality in consequence of which an electric
   charge tends to discharge itself, as into the air by a
   spark, or to pass from a body of greater to one of less
   electrical potential. It varies as the quantity of
   electricity upon a given area.
{Tension brace}, or {Tension member} (Engin.), a brace or
   member designed to resist tension, or subjected to
   tension, in a structure.
{Tension rod} (Engin.), an iron rod used as a tension member
   to strengthen timber or metal framework, roofs, or the
   like.