The concept of determiners is widely employed in linguistics, but mostly absent from English Language Teaching (ELT) materials (dictionaries, teacher-reference books, and student-oriented texts). Among those employing the concept, there is near-universal confusion between determiners and pronouns, arising mainly from an analytical and terminological failure to distinguish consistently between the category ("determinative") and the function ("specifier"). I criticize this situation and present linguistic evidence for a more consistent framework. I conclude by arguing that in language teaching and applied linguistics we rarely adopt advances from linguistics, not because they fail to meet some criterion of relevance a la Widdowson (2000), but simply because we are ignorant of linguistics in general.