The aim of this study is to delineate the functional category of English secondary determiners more precisely than in current reference grammars and in my own previous work. To provide a principled basis for a functional typology of secondary determiners, I firstly develop a typology of primary determiner (or ‘grounding’) types within the framework of Cognitive Grammar. Following Langacker, four main types are distinguished, and their referential and discursive properties are characterized: indefinite grounding, relative quantification, possessive grounding, and definite grounding. This typology then forms the starting point for drawing up a typology of the main types of instructions given by secondary determiners, i.e. to retrieve the type specifications of an instance newly introduced by an indefinite NP, to identify the correct antecedent of a definite NP, to relate a referent to another instance of the same type, or to refer to a generalized referent. Thirdly, modifier types that had been confused with secondary determiners in earlier work are distinguished from them on the basis of their semantics and formal behaviour, viz. focus markers, nominal aspectual modifiers, modal and temporal modifiers, and metadesignatives.