polysyllable vs word

polysyllable and word both are nouns.

Word	Noun	Adjective	Verb	Adverb
polysyllable	Yes	No	No	No
word	Yes	No	Yes	No

As nouns, word is a hypernym of polysyllable; that is, word is a word with a broader meaning than polysyllable:

polysyllable (noun)	word (noun)
a word of more than three syllables	a unit of language that native speakers can identify
	a promise
	information about recent and important events
	a brief statement
	an exchange of views on some topic
	a secret word or phrase known only to a restricted group
	a verbal command for action
	a string of bits stored in computer memory

polysyllable (verb)	word (verb)
	put into words or an expression