This chapter explored the influence of Celtic, Latin, Scandinavian, French, and other languages on Old and Middle English. Each of these languages has a unique relationship with English, noticeable in the kinds of words borrowed and in how the grammar is affected. French has an enormous influence on late Old and Middle English vocabulary, which makes Middle English look very different from Old English. Scandinavian influences the grammar, and we will see some possible consequences of that in the next chapter. We also talked about some of the issues related to the expanded vocabulary and discussed a scale to measure the levels of contact.