word vs voice communication

word and voice communication both are nouns.

Word	Noun	Adjective	Verb	Adverb
word	Yes	No	Yes	No
voice communication	Yes	No	No	No

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

word (noun)	voice communication (noun)
a unit of language that native speakers can identify	(language) communication by word of mouth
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 (verb)	voice communication (verb)
put into words or an expression