Diurn

Part of speech: adjective

Definitions

1. An archaic term for a single day or the period of daylight within it
2. An obsolete noun meaning one day, or the daytime portion of a twenty-four hour cycle
3. A rare, old-fashioned word denoting a day as a unit of time or a stretch of daylight

Etymology: Before "diurnal" was a standard English adjective, "diurn" was a clipped, now largely obsolete form of it, meaning "of the day" as opposed to the night. Both come from Latin "diurnus," built from "dies," "day," and the sense of daily recurrence has stayed attached to the root. That root has also produced two much more familiar English words. "Journal" and "journey" both descend from a Latin adjective "diurnalis," which passed through Old French "jornal" and "journée." A "journal" was originally a daily record or account, and a "journey" was first the distance one could travel in a single day, which explains why the two words feel so unrelated today.