inlet vs fjord

inlet and fjord both are nouns.

Word	Noun	Adjective	Verb	Adverb
inlet	Yes	No	No	No
fjord	Yes	No	No	No

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

inlet: an arm off of a larger body of water (often between rocky headlands)
fjord: a long narrow inlet of the sea between steep cliffs; common in Norway

Other hyponyms of inlet include cove, fiord, loch.

inlet (noun)	fjord (noun)
an opening through which fluid is admitted to a tube or container	a long narrow inlet of the sea between steep cliffs; common in Norway
an arm off of a larger body of water (often between rocky headlands)