double-decker vs motorcoach

double-decker and motorcoach both are nouns.

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

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

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

Other synonyms of double-decker include autobus, bus, charabanc, coach, jitney, motorbus, omnibus, passenger vehicle.

double-decker (noun)	motorcoach (noun)
a vehicle carrying many passengers; used for public transport	a vehicle carrying many passengers; used for public transport