EN
The article discusses the role of the age of onset of language acquisition in the early multilingualism. The differences between first language acquisition and adult second language acquisition have been established in the literature. The explanation of them is still under discussion. This paper aims at showing why the investigation of child second language acquisition is relevant for this issue. The presented neurolinguisitic and linguistic studies explore the nature of the differences between developmental patterns of language acquisition of children starting their exposure to the second language at different age. The results of the studies are shown to be consistent with the hypothesis assuming that many differences between various types of language acquisition are due to the different age of the onset of acquisition.