omnibus vs double-decker

omnibus and double-decker both are nouns.

Word	Noun	Adjective	Verb	Adverb
omnibus	Yes	Yes	No	No
double-decker	Yes	No	No	No

As nouns, omnibus and double-decker are synonyms defined as:

omnibus and double-decker: a vehicle carrying many passengers; used for public transport

Other synonyms of omnibus include autobus, bus, charabanc, coach, jitney, motorbus, motorcoach, passenger vehicle.

omnibus (noun)	double-decker (noun)
a vehicle carrying many passengers; used for public transport	a vehicle carrying many passengers; used for public transport
an anthology of articles on a related subject or an anthology of the works of a single author

omnibus (adjective)	double-decker (adjective)
providing for many things at once