Relating to something that occurs at an unspecified time or outside of normal chronological sequence.
From Greek 'a-' (without) + 'chronos' (time) + '-ical' (adjective suffix). Despite the 'a-' prefix suggesting 'without time,' the actual usage became more specific in astronomy regarding heliacal risings.
This word has an interesting history—it started meaning 'not at a specific time' but astronomers hijacked it for a specific technical meaning about when stars appear relative to the sun, showing how scientific jargon can flip meanings!
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