The adjective superfluous means something that is unnecessary or is no longer needed.

Synonyms are excessive, expendable, redundant, or useless.

The word origins from Latin (late 14th century) superfluus meaning “unnecessary”, literally meaning “overflowing, running over”, from superfluere meaning “to overflow”. It comes from super meaning “over” plus fluere meaning “to flow”.

In my opinion, a saint has no superfluous merit.

Her presence at the evening party was superfluous.

The caustic soda becomes superfluous, once the glue is cured.