This chapter looks at both standard and non-standard varieties of English. Within standard English, it considers varieties of English as a first language (ENL) and as an institutionalised second language (ESL). The chapter outlines research on the global spread of English with a focus on the following processes of change: dialect and language contact, isolation, globalization vs. localization. Dialect contact is discussed as a major force in the development of ENL varieties in the US, Canada, New Zealand and Australia. The second half of the twentieth and the beginning of the twenty-first century are characterized by large-scale migration to ENL countries, not only from the former colonies of Britain and the US but also from non-English speaking parts of the world. A discussion of dialect contact thus also needs to take into account the possibility of secondary dialect contact, i.e. the influence of ESL varieties and the use of English as a foreign language on ENL varieties of English. An obvious outcome of language contact are the various pidgins and English-based creoles. However, language contact is also an important aspect of nativization and thus the development of ESL varieties in India, Singapore and Africa. During earlier periods in the global spread of English, the (relative) isolation of speakers is likely to have lead to the divergence of the different regional Englishes while the more recent re-establishment of contact especially via mass media has, to some extent, lead to a re-convergence of the New Englishes. Language and dialect contact via the mass media lead to globalization of features whereas local identity construction would be a force that leads to the development of more localized norms of language use. The discussion of these two competing factors includes the question as to how diffusion of change may work on a global scale and how globalization relates to supra-regionalization.