Bridging the gap between the fields of World Englishes and Second Language Acquisition, this volume offers an in-depth comparative analysis of two postcolonial varieties of English (Singapore and Malaysian English) and neighbouring Indonesian learner English in order to examine the Outer/Expanding Circle distinction and shed light on the genesis of postcolonial varieties of English. The study identifies and analyses more than thirty linguistic features in the categories phonology, morphology, syntax, and discourse, concluding that in spite of clear syntactic differences, the distinction between the Outer and Expanding Circles is gradual rather than strictly categorical, and should rely on current sociolinguistic realities rather than on historical criteria. The volume will be highly relevant for researchers interested in the dynamics of Outer Circle and Expanding Circle Englishes, the structural and sociolinguistic aspects of English in Southeast Asia, or the integration of the paradigms of World Englishes and Second Language Acquisition.