pregnancy test vs bio-assay

pregnancy test and bio-assay both are nouns.

Word	Noun	Adjective	Verb	Adverb
pregnancy test	Yes	No	No	No
bio-assay	Yes	No	No	No

As nouns, bio-assay is a hypernym of pregnancy test; that is, bio-assay is a word with a broader meaning than pregnancy test:

pregnancy test: a physiological test to determine whether a woman is pregnant
bio-assay: appraisal of the biological activity of a substance by testing its effect on an organism and comparing the result with some agreed standard

Other hypernyms of pregnancy test include bioassay.

pregnancy test (noun)	bio-assay (noun)
a physiological test to determine whether a woman is pregnant	appraisal of the biological activity of a substance by testing its effect on an organism and comparing the result with some agreed standard