Produced, originating or growing from within.
Of a natural process: caused by factors within the body.
Situated, produced, secreted in, or coming from inside an organ, tissue, muscle or member.
Built-in.
Innate, inherent, inseparable from the thing itself, essential.
A built-in function that is implemented directly by the compiler, without any intermediate call to a library.
An ability possessed by a character and not requiring any external equipment.