Definition of protolanguage in English:
 protolanguage
nounˈprəʊtəʊˌlaŋɡwɪdʒˈprōdōˌlaNG(ɡ)wij
A hypothetical lost parent language from which actual languages are derived.
 Example sentencesExamples
-  From a linguistic perspective, any protolanguage would be merely embryonic.
 -  His possible answer to this is that ‘the socio-cultural transition from protolanguages to modern languages took 60,000 years; but this seems unlikely in the light of modern evidence from creolization’ .
 -  This claim would be supported by a demonstration that linguistic behavior during sleep is restricted to protolanguage.
 -  Here we have to turn to notions of exaptation, for language is a unique aptitude that doesn't seem to have emerged from protolanguage, and certainly did not do so directly.