seaport vs harbour

seaport and harbour both are nouns.

Word	Noun	Adjective	Verb	Adverb
seaport	Yes	No	No	No
harbour	Yes	No	Yes	No

As nouns, seaport and harbour are synonyms defined as:

seaport and harbour: a sheltered port where ships can take on or discharge cargo

Other synonyms of seaport include harbor, haven.

seaport (noun)	harbour (noun)
a sheltered port where ships can take on or discharge cargo	a place of refuge and comfort and security
	a sheltered port where ships can take on or discharge cargo

seaport (verb)	harbour (verb)
	maintain (a theory, thoughts, or feelings)
	hold back a thought or feeling about
	keep in one's possession; of animals
	secretly shelter (as of fugitives or criminals)