choo-choo vs engine

choo-choo and engine both are nouns.

Word	Noun	Adjective	Verb	Adverb
choo-choo	Yes	No	No	No
engine	Yes	No	No	No

As nouns, engine is a hypernym of choo-choo; that is, engine is a word with a broader meaning than choo-choo:

choo-choo: a child's word for locomotive
engine: a wheeled vehicle consisting of a self-propelled engine that is used to draw trains along railway tracks

Other hypernyms of choo-choo include locomotive, locomotive engine, railway locomotive.

choo-choo (noun)	engine (noun)
a child's word for locomotive	motor that converts thermal energy to mechanical work
	a wheeled vehicle consisting of a self-propelled engine that is used to draw trains along railway tracks
	an instrument or machine that is used in warfare, such as a battering ram, catapult, artillery piece, etc.
	something used to achieve a purpose