Nighttime is the period when the sun has set and darkness covers your part of the earth. It begins at dusk, when the last rays of sunlight fade, and ends at dawn, when the sun rises again.

Nighttime happens because the earth rotates like a spinning top. As your location spins away from the sun, you enter the earth's shadow. That's nighttime. While you're experiencing nighttime, people on the opposite side of the planet are experiencing daytime.

For most of human history, nighttime meant stopping work and going to sleep, since people had only firelight to see by. The invention of electric lighting in the late 1800s changed everything, allowing people to read, work, and travel safely after dark. Today, many cities are so brightly lit at nighttime that you can barely see the stars.

Different creatures are active at different times. Nocturnal animals like owls and bats do most of their hunting at nighttime, while diurnal animals like most birds are active during the day. Humans are naturally diurnal, which is why staying up too late can make you tired the next morning.

The word can also be written as two words: night time.