Able to be moved toward and to touch other fingers or digits, especially the thumb—a rare ability that only certain animals have.
From Latin 'opponere' (to place against) combined with the suffix '-able' (capable of). 'Opposable' entered English in the 18th century to describe specific anatomical features, particularly the thumbs of primates that can press against other fingers.
Humans, apes, and some monkeys have opposable thumbs, but so do possums, koalas, and giant pandas—and it independently evolved in each group! This ability is so powerful for tool use that some scientists think it's one of the main reasons primates became so successful.
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