word of honor vs word

word of honor and word both are nouns.

Word	Noun	Adjective	Verb	Adverb
word of honor	Yes	No	No	No
word	Yes	No	Yes	No

As nouns, word of honor and word are synonyms defined as:

Other synonyms of word of honor include parole.

word of honor (noun)	word (noun)
a promise	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

word of honor (verb)	word (verb)
	put into words or an expression