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.