pang vs labour pains

pang and labour pains both are nouns.

Word	Noun	Adjective	Verb	Adverb
pang	Yes	No	No	No
labour pains	Yes	No	No	No

As nouns, labour pains is a hyponym of pang; that is, labour pains is a word with a more specific, narrower meaning than pang:

pang: a sharp spasm of pain
labour pains: a regularly recurrent spasm of pain that is characteristic of childbirth

Other hyponyms of pang include birth pangs, labor pains, afterpains.

pang (noun)	labour pains (noun)
a sudden sharp feeling	a regularly recurrent spasm of pain that is characteristic of childbirth
a sharp spasm of pain
a mental pain or distress