/ ˌiːkwɪˈnɒkʃl; ˌek-; NAmE -ˈnɑːk-/ adjective
connected with an equinox
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WORD ORIGIN
late Middle English (in the sense relating to equal periods of day and night ): via Old French from Latin aequinoctialis , from aequinoctium , from aequi- equal + nox , noct- night.