This book investigates phonological vowel patterns, that is, restrictions on which vowel sounds can occur where in a language. Such patterns intersect with two main themes of this work, characterized in (1).

1. (1) a. How word position affects the way in which vowels function in a pattern.

2. b. How aspects of the perception and production of speech affect vowel patterns.

Vowel patterns that interact with word position are pervasive in language. For example, many languages show some form of systematic reduction in the range of distinctive vowel qualities in unstressed syllables. This type of pattern occurs in languages such as Russian, Italian, and English. Instances of vowel reduction processes are witnessed when stress shifts under affixation. In Standard American English, primary stress (signified by an accent) is assigned to the first syllable in phótograph, where the vowel is pronounced as [ο℧]. In the related word, photógraphy, where stress is assigned to the second syllable, the pronunciation of the vowel in the first syllable is reduced to [ә], designating a mid-central quality that often occurs in unstressed syllables in all forms of English (Ladefoged 1993: 84f.). Other vowel qualities can reduce to [ә] in an unstressed syllable, as in expláin [еɪ] versus explanátion [ә] or emphátic [æ] versus émphasis [ә], causing a number of vowel distinctions to be merged in some unstressed contexts.