language unit vs phone

language unit and phone both are nouns.

Word	Noun	Adjective	Verb	Adverb
language unit	Yes	No	No	No
phone	Yes	No	Yes	No

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

language unit: one of the natural units into which linguistic messages can be analyzed
phone: (phonetics) an individual sound unit of speech without concern as to whether or not it is a phoneme of some language

Other hyponyms of language unit include discourse, word, syllable, lexeme, morpheme, formative, name, collocation, sound, speech sound, sign.

language unit (noun)	phone (noun)
one of the natural units into which linguistic messages can be analyzed	electronic equipment that converts sound into electrical signals that can be transmitted over distances and then converts received signals back into sounds
	electro-acoustic transducer for converting electric signals into sounds; it is held over or inserted into the ear
	(phonetics) an individual sound unit of speech without concern as to whether or not it is a phoneme of some language

language unit (verb)	phone (verb)
	get or try to get into communication (with someone) by telephone