Anything (such as a piece of furniture, or a software feature) that is built in, not added as an extra.
Being an essential and permanent part of something.
Being an included feature that normally comes as an extra.
Constructed as a non-detachable part of a larger structure.
A temporary variable.
One serving for a limited time; short-term employee.
Existing only for a short time or short times; transient, ephemeral.
Not permanent; existing only for a period or periods of time.