In a 21st-century super-diverse world, young children are likely to speak different first languages which are not the majority language of society. For some children, preschool is one of the few environments where they experience this majority language. A pressing issue encountered by preschool teachers is how to communicate with these children and how to help these children acquire the majority language they need for a successful school entry. Building a repertoire of words in the majority language is one of the first steps. Strategies that monolingual children use to map words to their referents in the environment have been of interest for 60 years. However, less is known about the early development of word learning in bilingual children. This thesis, therefore, seeks to understand how monolingual and bilingual children utilise different strategies to learn words using experimental methods and look at how preschool teachers communicate with children in a preschool setting via naturalistic observation. The ultimate goal of this thesis is to identify and develop strategies that preschool teachers can use to foster children’s development of the majority language.

In two experimental studies, this thesis examined (1) how monolingual and bilingual preschoolers learn words from speakers of different languages through mutual exclusivity and the acceptance of lexical overlap, and (2) whether and how socio-pragmatic cues influence monolingual and bilingual language learners’ learning of one-to-one and two-to-one word-object mappings through cross-situational statistics. In two observational studies, this thesis looked into whether and how preschool teachers in a UK setting communicated differently with monolingual preschoolers and preschoolers learning English as an additional language (EAL). The thesis also set out to identify the linguistic features of preschool talk that could predict preschoolers’, especially EAL children’s, language development.

The findings of the experimental studies show a complex interaction between the different word-learning strategies and prior language experience, and the results suggest that word-learning strategies available to monolingual and bilingual learners are the same but used differently. The findings of the observational studies show that preschool teacher talk to EAL children, in terms of lexical diversity and syntactic complexity, affects the children’s development of English, suggesting that preschool teachers’ language use could scaffold and support EAL children’s acquisition of English. The findings of this thesis suggest that matching language input to EAL children’s English level and setting up learning situations that closely mimic those of bilingual word learning may be helpful strategies for preschool teachers to support EAL children’s English development.