1) Twelve pairs of nerves that carry general afferent, visceral afferent, special afferent, somatic efferent, and autonomic efferent fibers.

2) Any of the 12 paired nerves that originate in the brain stem.

3) Any of the 12 paired nerves that arise from the lower surface of the brain with one of each pair on each side and pass through openings in the skull to the periphery of the body.