A vocabulary of landscape — a landscape of words
1133 entries
crepuscule
Crepuscule is twilight, the period when the sun is below the horizon but the sky is still lit by sunlight bent and scattered through the upper atmosphere. It is divided into three stages by how far down the sun has gone: civil twilight, when you can still work outside; nautical twilight, when the horizon is still visible against the sky and stars are out, which is when a sextant works; and astronomical twilight, after which the sky is as dark as it will get.
Etymology
The word comes from Latin for dusk, built on a root meaning dark or dim. Its main use in English now is the adjective, and crepuscular is a working term in wildlife biology for animals active at dawn and dusk rather than by day or by night. Deer, rabbits, coyotes, bobcats, and most bats are crepuscular.
Notes
The three stages are defined by the sun’s depth below the horizon at six, twelve, and eighteen degrees. Above roughly 60 degrees latitude, astronomical twilight never fully ends around midsummer, so the sky does not reach true darkness for weeks. The word is used more in French than in English, where crépuscule is the ordinary term for dusk.