coupling vs coupler

coupling and coupler both are nouns.

Word	Noun	Adjective	Verb	Adverb
coupling	Yes	No	No	No
coupler	Yes	No	No	No

As nouns, coupling and coupler are synonyms defined as:

coupling and coupler: a mechanical device that serves to connect the ends of adjacent objects

coupling (noun)	coupler (noun)
the act of pairing a male and female for reproductive purposes	a mechanical device that serves to connect the ends of adjacent objects
a mechanical device that serves to connect the ends of adjacent objects
a connection (like a clamp or vise) between two things so they move together