Being only in between other more important things; secondary, incidental.(adjective)
Intervening, interceding, placed or coming between.(adjective)
One who intervenes.(noun)
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Use "intervenient" in a sentence
"If by the presence of such a body, then there will be vision though there be no intervenient; if the intervenient is the sole attractive agent, then we are forced to think of the visible object as being a Kind utterly without energy, performing no act."
"For if the intervenient appetites make any action voluntary, then by the same reason all intervenient aversions should make the same action involuntary; and so one and the same action should be both voluntary and involuntary."
"Therefore it is an happy thing in a state, when kings and states do often consult with judges; and again, when judges do often consult with the king and state: the one, when there is matter of law, intervenient in business of state; the other, when there is some consideration of state, intervenient in matter of law."