interlanguage vs koine

interlanguage and koine both are nouns.

Word	Noun	Adjective	Verb	Adverb
interlanguage	Yes	No	No	No
koine	Yes	No	No	No

As nouns, interlanguage and koine are synonyms defined as:

interlanguage and koine: a common language used by speakers of different languages

Other synonyms of interlanguage include lingua franca.

interlanguage (noun)	koine (noun)
a common language used by speakers of different languages	a common language used by speakers of different languages