The term background can have any of the following meanings:

• Background (computer software) refers to software that is running, but not being displayed.
• Background (astronomy) refers to small amounts of light coming from otherwise dark parts of the sky.
• Background radiation refers to the natural radiation that is always present in a location.
• Cosmic microwave background radiation is a natural constant radiation emanating throughout the universe.
• Background (journalism) is an understanding between a news source and a reporter on the privacy of a discussion.