Phonology provides a system by which a limited number of types of phonetic variation can signal communicative intentions at multiple levels of linguistic analysis. Because phonologies vary from language to language, acquiring the phonology of a language demands learning to attribute phonetic variation appropriately. Here, we studied the case of pitch-contour variation. In English, pitch contour does not differentiate words, but serves other functions, like marking yes/no questions and conveying emotions. We show that, in accordance with their phonology, English-speaking adults and 2-year-olds do not interpret salient pitch contours as inherent to novel words. We taught participants a new word with consistent segmental and pitch characteristics, and then tested word recognition for trained and deviant pronunciations using an eyegaze-based procedure. Vowel-quality mispronunciations impaired recognition, but large changes in pitch contour did not. By age 2, children already apply their knowledge of English phonology to interpret phonetic consistencies in their experience with words. (Contains 4 tables and 5 figures.)