carriage vs hackney

carriage and hackney both are nouns.

Word	Noun	Adjective	Verb	Adverb
carriage	Yes	No	No	No
hackney	Yes	No	No	No

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

carriage (noun)	hackney (noun)
a vehicle with wheels drawn by one or more horses	a compact breed of harness horse
a railcar where passengers ride	a carriage for hire
a machine part that carries something else
a small vehicle with four wheels in which a baby or child is pushed around
characteristic way of bearing one's body