1 : depending on individual discretion (as of a judge) and not fixed by law
3 a : based on or determined by individual preference or convenience rather than by necessity or the intrinsic nature of something
b : existing or coming about seemingly at random or by chance or as a capricious and unreasonable act of will
"Most of The Economist's style book entry on hyphens consists of seemingly arbitrary rulings on disputable cases: 'non-existent' but 'nonaligned,' 'arch-rival,' but 'archangel.' … The overarching rule is that, at the very least, you should be consistent, so that readers don't find 'arch-rival' and 'archrival' on the same page." — The Economist, 10 June 2017
Did You Know?
Arbitrary is derived from the same source as arbiter. The Latin word arbiter means "judge," and English adopted it, via Anglo-French, with the meaning "one who judges a dispute"; it can now also be used for anyone whose judgment is respected. Arbitrary traces back to the Latin adjective arbitrarius ("done by way of legal arbitration"), which itself comes from arbiter. In English arbitrary first meant "depending upon choice or discretion" and was specifically used to indicate the sort of decision (as for punishment) left up to the expert determination of a judge rather than defined by law. Today, it can also be used for anything determined by or as if by a personal choice or whim.
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