1. noun /bɜː(ɹ)θ/
a) The process of childbearing.

He was of noble birth, but fortune had not favored him.

b) An instance of childbirth.
2. adjective /bɜː(ɹ)θ/
A familial relationship established by childbirth.

Her birth father left when she was a baby; she was raised by her mother and stepfather.

3. verb /bɜː(ɹ)θ/
a) To bear or give birth to (a child).

Biological evolution created a human mind that enabled cultural evolution, which now outpaces and outclasses the force that birthed it.

Wikipedia foundation.