omnibus vs minibus

omnibus and minibus both are nouns.

Word	Noun	Adjective	Verb	Adverb
omnibus	Yes	Yes	No	No
minibus	Yes	No	No	No

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

Other hyponyms of omnibus include school bus, trackless trolley, trolley coach, trolleybus.

omnibus (noun)	minibus (noun)
a vehicle carrying many passengers; used for public transport	a light bus (4 to 10 passengers)
an anthology of articles on a related subject or an anthology of the works of a single author

omnibus (adjective)	minibus (adjective)
providing for many things at once