Definition of "Day" :

noun: United States writer best known for his autobiographical works (1874-1935)

noun: a period of opportunity

"He deserves his day in court."

noun: some point or period in time

"It should arrive any day now."

noun: the recurring hours when you are not sleeping (especially those when you are working)

"My day began early this morning."

noun: time for Earth to make a complete rotation on its axis

"Two days later they left."

noun: a day assigned to a particular purpose or observance

"Mother's Day."

noun: the time after sunrise and before sunset while it is light outside

"The dawn turned night into day."

noun: the time for one complete rotation of the earth relative to a particular star, about 4 minutes shorter than a mean solar day

noun: the period of time taken by a particular planet (e.g. Mars) to make a complete rotation on its axis

"How long is a day on Jupiter?."

noun: an era of existence or influence

"In the day of the dinosaurs."