bearing vs fifth wheel

bearing and fifth wheel both are nouns.

Word	Noun	Adjective	Verb	Adverb
bearing	Yes	Yes	No	No
fifth wheel	Yes	No	No	No

As nouns, fifth wheel is a hyponym of bearing; that is, fifth wheel is a word with a more specific, narrower meaning than bearing:

bearing: a rotating support placed between moving parts to allow them to move easily
fifth wheel: a steering bearing that enables the front axle of a horse-drawn wagon to rotate

Other hyponyms of bearing include ball bearing, needle bearing, roller bearing, journal bearing, thrust bearing.

bearing (noun)	fifth wheel (noun)
a rotating support placed between moving parts to allow them to move easily	a steering bearing that enables the front axle of a horse-drawn wagon to rotate
heraldry consisting of a design or image depicted on a shield	an extra car wheel and tire for a four-wheel vehicle
dignified manner or conduct	someone or something that is unwanted and unneeded
characteristic way of bearing one's body
the direction or path along which something moves or along which it lies
relevant relation or interconnection

bearing (adjective)	fifth wheel (adjective)
(of a structural member) withstanding a weight or strain