A/an and the: allomorphy or phonology?
English <em>a/an</em> presents a well-known paradox: it is restricted to a single morpheme, which suggests that it is a morphological phenomenon, yet it depends crucially on information about the <em>following</em> word, and thus cannot be characterized as a strictly word-internal process. Here I look at <em>a/an </em>alongside a strikingly similar but far less studied alternation: English definite article th/i/ vs. th/ə/. I argue that despite initial appearances, neither <em>a/an</em> nor <em>thi/t</em><em>hə</em> is determined by syllable well-formedness constraints. I show parallels between the two cases that can be explained under a phonological treatment featuring a vowel-reduction rule, which applies to both <em>thi</em> and the ‘strong’ <em>a/an</em> form /ej/.