by day(redirected from by night)
During the day. Often used to refer to one's employment or other typical daytime activities, in contrast with what they are apt to do "by night." By day, he was an average office clerk, but by night he was crime-fighting vigilante. She's a teacher by day and an actress at the local theater by night.
by dayand by night
during the day; during the night. (Often used in simultaneous clauses for contrast.) By day, Mary worked in an office; by night, she took classes. Dave slept by day and worked by night.