Embelian

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An embelian is a unitian in which individual members already existed before the unit as separate members, and only unify under certain circumstances, often willingly. Because of this, they may be together often, or hardly at all, depending on if it’s currently needed.

Members in embelians may not be part of the same subsystem/layer/etc., and may or may not have any relation to each other outside of their embelian.

The adjective is "embelic” and can be used to describe systems as well (ex: an embelic subsystem).

Related Terms
The terms sevarian, pazlian, and condrian also fall under unitian.