biology vs astrobiology

biology and astrobiology both are nouns.

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

As nouns, astrobiology is a hyponym of biology; that is, astrobiology is a word with a more specific, narrower meaning than biology:

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

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