Null
The value null is a reference that does not refer to anything.
Related concepts: ValueReference
Closest Wikipedia entry: Null pointer
Misconceptions about Null7 documented Misconceptions
Check YourselfBoxedNull — Java
Passing null to a wrapper class constructor creates an object representing the absence of a valueNullAndUndefinedAreTheSame — JavaScript
The values null and undefined are the sameNullIsObject — Java
null is an objectNullIsObject — JavaScript
null is an objectOutOfBoundsElementsAreNull — Java
Out-of-bounds array elements are nullThisCanBeNull — Java
this can be nullThisInConstructorIsNull — Java
In a constructor, this is null