One of the major goals of the Cambridge English Profile Programme is to identify ‘criterial features’ for each of the Common European Framework of Reference (CEFR) proficiency levels as they apply to English, and to assess the impact of different first languages on these features (through ‘transfer’ effects). The present paper defines what is meant by criterial features and proposes an initial taxonomy of four types. Numerous illustrations are given from our collaborative research to date on the Cambridge Learner Corpus. The benefits and challenges posed by these features for corpus linguistics and for theories of second language acquisition are briefly outlined, as are the benefits and challenges for language assessment practices and for publishing ventures that make use of them as supplements to the current CEFR descriptors.
