Definition of "inclusion"

inclusion

/ɪnˈkluːʒən/

noun
countable and uncountable, plural inclusions
1. (countable) An addition or annex to a group, set, or total.
2. (uncountable) The act of including, i.e. adding or annexing, (something) to a group, set, or total.
3. (countable) Anything foreign that is included in a material,
4. (countable, mineralogy) Any material that is trapped inside a mineral during its formation, as a defect in a precious stone.
  Quotations
  The fewer inclusions a diamond has, the better is its clarity and value. Often the inclusions can be cut out of a diamond in the rough.
  2009, Cindy Lasiter, Diamonds in the Rough, Xulon Press, page xi
5. (cytology) A nuclear or cytoplasmic aggregate of stainable substances.
6. (histology) An object completely inside a tissue, such as epidermal inclusion cyst, a cyst in the epidermis.
7. (mathematics) A mapping where the domain is a subset of the image.
8. (obsolete) Restriction; limitation.