Inclusion

noun

1. An addition or annex to a group, set, or total.

   "The poem was a new inclusion in the textbook."

2. The act of including, i.e. adding or annexing, (something) to a group, set, or total.

   "The inclusion of the poem added value to the course."

3. Anything foreign that is included in a material,
4. Any material that is trapped inside a mineral during its formation, as a defect in a precious stone.
5. A nuclear or cytoplasmic aggregate of stainable substances.