Chapter 11 brings together the main thread running through the book: how first language backgrounds influence multilingual lexicons. Script differences between the first and subsequent languages are seen to influence how learners read and process lexis. Such differences affect the processing of language in terms of the use of phonology, semantics, and syntax. Language production, translation, and writing are summarised and first language background is found to influence priming asymmetry effects in different language directions. First language typology is also found to relate to formulaic sequences and collocations in subsequent languages. Translation can also be used to help learners discover “difficult” language items. The chapter ends with vocabulary assessment. The cognate relationship between languages is analysed to help inform test designers to create valid vocabulary tests.