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c.1600, from Latin inclusionem (nominative inclusio) "a shutting up, confinement," noun of action from past participle stem of includere (see include).
inclusion in·clu·sion (ĭn-klōō'zhən)n.
A nonliving mass, such as a droplet of fat, in the cytoplasm of a cell.
The process by which a foreign or heterogenous structure is misplaced in another tissue.