Real Dictionary

background
a horizontal datum line or plane [...]
any sign, gesture, token, etc, that serves to communicate information [...]
the act or process of subtracting [...]
The background to an event or situation consists of the facts that explain what caused it.
the emission of light or other radiation from atoms or molecules that are bombarded by particles, such as electrons, or by radiation from a separate source. The bombarding radiation produces excited atoms, molecules, or ions and these emit photons as they
the part of a scene or view furthest from the viewer [...]
Your background is the kind of family you come from and the kind of education you have had. It can also refer to such things as your social and racial origins, your financial status, or the type of work experience that you have.
singular noun: The background is sounds, such as music, which you can hear but which you are not listening to with your full attention.