Cranial nerve and Second cranial nerve

Cranial nerve noun - Any of the 12 paired nerves that originate in the brain stem.

Second cranial nerve and cranial nerve are semantically related. In some cases you can replace phrase "Second cranial nerve" with "Cranial nerve", this phrases are similar.

Second cranial nerve noun - The cranial nerve that serves the retina.

Cranial nerve and second cranial nerve are semantically related. You can use "Cranial nerve" instead a noun phrase "Second cranial nerve".