serum vs bodily fluid

serum and bodily fluid both are nouns.

Word	Noun	Adjective	Verb	Adverb
serum	Yes	No	No	No
bodily fluid	Yes	No	No	No

As nouns, bodily fluid is a hypernym of serum; that is, bodily fluid is a word with a broader meaning than serum:

serum: an amber, watery fluid, rich in proteins, that separates out when blood coagulates
bodily fluid: the liquid parts of the body

Other hypernyms of serum include body fluid, humor, humour, liquid body substance.

serum (noun)	bodily fluid (noun)
an amber, watery fluid, rich in proteins, that separates out when blood coagulates	the liquid parts of the body