blood serum vs body fluid

blood serum and body fluid both are nouns.

Word	Noun	Adjective	Verb	Adverb
blood serum	Yes	No	No	No
body fluid	Yes	No	No	No

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

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

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

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