A nightlight is a small light fixture

Light fixture

A light fixture, light fitting, or luminaire is an electrical device used to create artificial light and/or illumination, by use of an electric lamp...

, often electrical, placed for comfort or convenience in dark areas or areas that become dark at certain times, such as in an emergency

Emergency light

An emergency light is a battery-backed lighting device that comes on automatically when a building experiences a power outage. Emergency lights are standard in new commercial and high occupancy residential buildings, such as college dormitories...

. Small long-burning candles serving a similar function are referred to as tealight

Tealight

A tealight , or nightlight, is a candle encased in a thin metal or plastic cover so that the candle can liquefy completely while lit. They are typically small, circular, wider than their height and inexpensive...

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People often use nightlights for the sense of security which having a light on provides, and for a solution against nyctophobia

Nyctophobia

Nyctophobia is a phobia characterized by a severe fear of the darkness. It is triggered by the brain’s disfigured perception of what would or could happen when in a dark environment....

 (fear of the dark). Besides their usefulness to children in the allaying of their fears, nightlights are also useful to the general public by showing the general layout of a room without turning on a major light, for avoiding tripping over stairs or obstacles, or to mark an emergency exit.