Day
Part of speech: noun
Definition: A period of 24 hours. The period from midnight to the following midnight. There are 7 days in a week: Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, and Saturday. Rotational period of a planet (especially earth). The part of a day period which one spends at one's job, school, etc. Part of a day period between sunrise and sunset where one enjoys daylight, daytime.
Night
Part of speech: noun
Definition: The period between sunset and sunrise, when a location faces far away from the sun, thus when the sky is dark.An evening or night spent at a particular activity.A night (and part of the days before and after it) spent in a hotel or other accommodation.The quality of sleep obtained during a night.Nightfall.Darkness.
Part of speech: interjection
Definition: Short for good night