dispositive \dih-SPOZ-i-tiv\,
adjective:
involving or affecting disposition or settlement: a dispositive clue in a case of embezzlement.
Perhaps it had been a hallucination, or it was a false memory. Boggs had even predicted that later Ellis would doubt the incident had even happened—which seemed dispositive toward the dead man's reality…
-- Nick Arvin, "The Reconstructionist," 2012
Looks and charm were often dispositive, the more attractive partner sailing on to other waters.
-- Louis Begley, "About Schmidt," 1996
Dispositive comes from the word dispose meaning "to put in a particular place."
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