Null

Null is the computer representation of nothing.

Uses [edit]

In a relational database a null value typically represents an unset field for a record.
In some programming languages null is the default value of an unset variable. Null can also be used to unset a variable which was previously pointing to an object.
The null device on a Unix-like operating system points to nothing. Data can be directed to /dev/null to disappear.