crepuscular

Merriam-Webster's Word of the Day for March 8, 2026 is: crepuscular \krih-PUHSS-kyuh-ler\ adjective Crepuscular means “of, relating to, or resembling twilight.” It is used in zoological contexts to describe creatures that are active during twilight, or the activities of such creatures. // As evening came on, fireflies began to appear in the crepuscular [gloaming](https://www.merriam-webster.com/dictionary/gloaming). [See the entry >](https://www.merriam-webster.com/dictionary/crepuscular) Examples: “To gaze upon a platypus is to witness a jumble of contradictions. … Even when you see one with your own eyes—say, paddling underwater, absorbed in her crepuscular rooting—the platypus (Ornithorhynchus anatinus) remains hard to believe.” — Kathleen Yale, Orion, Winter 2025/2026 Did you know? The early Romans had two words for the twilight. Crepusculum was favored by Roman writers for the half-light of evening, just after the sun sets; diluculum was reserved for morning twilight, just before the sun rises—it is related to lūcidus, meaning “bright.” (Crepusculum was likely modeled on diluculum, from the assumed root krepos-, meaning “twilight.”) English speakers didn’t embrace either of these Latin nouns as substitutes for the word [twilight](https://www.merriam-webster.com/dictionary/twilight), but they did form the adjective crepuscular in the 17th century. The word’s zoological sense, relating to animals that are most active at twilight, developed in the 19th century.