autobus vs trolleybus

autobus and trolleybus both are nouns.

Word	Noun	Adjective	Verb	Adverb
autobus	Yes	No	No	No
trolleybus	Yes	No	No	No

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

autobus: a vehicle carrying many passengers; used for public transport
trolleybus: a passenger bus with an electric motor that draws power from overhead wires

Other hyponyms of autobus include minibus, school bus, trackless trolley, trolley coach.

autobus (noun)	trolleybus (noun)
a vehicle carrying many passengers; used for public transport	a passenger bus with an electric motor that draws power from overhead wires