Interest in linguistic alternatives was triggered by Labov’s sociolinguistic studies in the early 1960s, which showed that linguistic variation was not random but systematic. Typically, one of the variants is regarded as the default and the others as deviations. This introduction presents an approach to syntactic variation from the perspective of (non‑)canonicity. It first approaches the term ‘non-canonical’ from a morphological and etymological perspective before outlining the frequency- and the theory-based approaches to the notion. The introduction then defines as a canonical syntactic construction a default which under general circumstances will be chosen with the highest likelihood, while any deviation from the default is called ‘non-canonical’. The paper classifies these deviations into five basic but combinable types. While the status of one variant as default is typically stable in research on syntactic variation, research on syntactic (non‑)canonicity places particular emphasis on the elusive character of canonicity depending on, for instance, the variety, register, or mode of English. Thus, an infrequent deviation from the basic SXV order like topicalisation is clearly non-canonical in Standard British English but may well be canonical in another regional variety like Indian English. An overview of the structure of the volume concludes the introduction.

This synopsis rounds off the collected volume by summarising the main findings with regard to the concepts, approaches, and methods in studies on (non-)canonical syntax: First, the contributions corroborate the ubiquity of non-canonical syntax – a phenomenon which occurs in all areas of language use. The synopsis then refers back to the definition of the concept of (non‑)canonicity provided in the Introduction to the volume. The contributions to the volume, however, show that both the existence of neighbouring alternatives and the functions of non-canonical constructions are of importance when it comes to understanding non-canonical syntax and its longevity, despite its rarity. This demonstrates that a combination of the theory- and the frequency-based approaches is indeed essential. The synopsis also discusses the predominance of empirical and corpus-based approaches to the study of syntactic (non‑)canonicity, but also emphasises the merits of methodological pluralism, before it finally specifies a number of desiderata for future research into syntactic (non-)canonicity.