Many factors can influence the children’s success in learning the second language. Being brought up in the bilingual family, a person can develop speech skills in both languages simultaneously or in sequence. That is why, both languages can affect each other because of similarities or differences in their structures and semantics. Family and school environments are important to affect the process of learning two languages. Thus, the degree of the second language learning and acquisition can be assessed with references to the number and character of errors made by the learner while using the second language for communicating with the other people. During the process of acquisition of two languages, a child can make developmental errors, transfer errors, and mix languages while communicating orally, and the character of these errors can be analyzed in order to make conclusions about the level of the second language acquisition. When a child is brought up in the family where parents use two languages to communicate with each other the child can make definite errors and mix languages while attempting to present his or her thought because these two languages used within the common environments can influence each other. Developmental errors are characteristic for a person when two languages are learnt simultaneously or when a child at the first stage of learning the second language (Paradis, Genesee, & Crago, 2011). Developmental errors are the speech mistakes which can be made by any young person because the basics of the language are not learnt fully, and only the first efforts to use the second language correctly are made by a child. Thus, it is possible to state that developmental errors are rather natural in their character because they are not caused by the impact of the other language (Paradis, Genesee, & Crago, 2011, p. 265). The examples of such errors are the wrong word order, grammatical mistakes, and the omission of morphemes. For instance, the child omits verbs and some prepositions and changes the word order because of lacking the necessary knowledge about definite grammatical rules. There can be errors in using the endings of words in relation to plurals or possessive cases (“then I said yes and then not my friends and then they ask me to be their friends again”) (Chloe, personal communication, 2013). From this perspective, a child can formulate the phrase or sentence inappropriately according to their structure because of omitting some important details such as the word order of subjects and predicates. Thus, the child can say ‘sever’ instead of ‘civil’ or ‘paying’ instead of ‘playing’ as a result of confusing words (Chloe, personal communication, 2013). These errors are caused by the similarities in the words’ pronunciation, but they are not affected by the particular features of the other language in which the learner can be more competent. That is why, these errors can be discussed as developmental ones. When errors in the learner’s speech are caused by the first language background these errors are discussed and analyzed as transfer errors. The role of transfer errors is important to examine and assess the level of the language acquisition from the point of the first language’s impact on the process of lea