Extension \Ex*ten"sion\, n. [L. extensio: cf. F. extension. See Extend, v. t.]

1. The act of extending or the state of being extended; a stretching out; enlargement in breadth or continuation of length; increase; augmentation; expansion.

2. (Physics) That property of a body by which it occupies a portion of space.

3. (Logic & Metaph.) Capacity of a concept or general term to include a greater or smaller number of objects; -- correlative of intension.

The law is that the intension of our knowledge is in the inverse ratio of its extension. --Sir W. Hamilton.

The extension of [the term] plant is greater than that of geranium, because it includes more objects. --Abp. Thomson.

4. (Surg.) The operation of stretching a broken bone so as to bring the fragments into the same straight line.

5. (Physiol.) The straightening of a limb, in distinction from flexion.

6. (Com.) A written engagement on the part of a creditor, allowing a debtor further time to pay a debt.

Counter extension. (Surg.) See under Counter.

Extension table, a table so constructed as to be readily extended or contracted in length.

Source: Webster's Revised Unabridged Dictionary (1913)