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. See the entry > 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, 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.