Parts of speech: Solid citizens or slippery customers?

The ‘parts of speech’ which have played a fundamental role in most descriptions of grammar, from primary school curriculum to advanced linguistic theory, are explored in this article, which considers some intriguing changes in recent everyday English that challenge traditional assumptions about the definition and usefulness of word classes such as ‘pronoun’, ‘adjective’ and ‘noun’. The article raises important questions about what happens at the boundaries between these word classes and looks at how we can answer these questions—potentially changing the direction of both future linguistic research and pedagogical practice.