The act of combining or joining things together; a combination formed by uniting elements.
From Old French accombiner, combining ad- (to) + combiner (to combine). The suffix -ation converts the verb into a noun indicating the process or result.
This word is pure redundancy—'combination' already means combining things, so adding the prefix 'ac-' creates no new meaning, which is probably why it completely vanished in favor of the simpler 'combination.'
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