specialization

noun

1. 1

   The act or process of specializing.

2. 2

   The area in which someone specializes.

3. 3

   The adaptation of an organism to a specific environment, or adaptation of an organ to a particular function.

4. 4

   A proof, axiom, problem, or definition whose cases are completely covered by another, broader concept.

   “A triangle is a specialization of a polygon to one with exactly three sides.”