word vs good word

word and good word both are nouns.

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

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

Other hyponyms of word include latest.

word (noun)	good word (noun)
a unit of language that native speakers can identify	good news
a promise	something that recommends (or expresses commendation of) a person or thing as worthy or desirable
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 (verb)	good word (verb)
put into words or an expression