Intension

Noun

1. intensity or the act of becoming intense.
2. Any property or quality connoted by a word, phrase or other symbol, contrasted with actual instances in the real world to which the term applies.

   "'Is a plant', 'has a trunk', 'has leaves' are intensions of the concept tree. Its extension is the set of all trees existing in the real world."

3. A straining, stretching, or bending; the state of being strained.

   "the intension of a musical string"