ology vs subject field

ology and subject field both are nouns.

Word	Noun	Adjective	Verb	Adverb
ology	Yes	No	No	No
subject field	Yes	No	No	No

As nouns, subject field is a hypernym of ology; that is, subject field is a word with a broader meaning than ology:

ology: an informal word (abstracted from words with this ending) for some unidentified branch of knowledge
subject field: a branch of knowledge

Other hypernyms of ology include bailiwick, discipline, field, field of study, study, subject, subject area.

ology (noun)	subject field (noun)
an informal word (abstracted from words with this ending) for some unidentified branch of knowledge	a branch of knowledge