astrobiology vs biology

astrobiology and biology both are nouns.

Word	Noun	Adjective	Verb	Adverb
astrobiology	Yes	No	No	No
biology	Yes	No	No	No

As nouns, biology is a hypernym of astrobiology; that is, biology is a word with a broader meaning than astrobiology:

astrobiology: the branch of biology concerned with the effects of outer space on living organisms and the search for extraterrestrial life
biology: the science that studies living organisms

Other hypernyms of astrobiology include biological science.

astrobiology (noun)	biology (noun)
the branch of biology concerned with the effects of outer space on living organisms and the search for extraterrestrial life	the science that studies living organisms
	all the plant and animal life of a particular region
	characteristic life processes and phenomena of living organisms