Stress and vowel reduction in English

Stress is a prominent feature of the English language, both at the level of the word (lexical stress) and at the level of the phrase or sentence (prosodic stress). Absence of stress on a syllable, or on a word in some cases, is frequently associated in English with vowel reduction – many such syllables are pronounced with a centralized vowel (schwa) or with certain other vowels that are described as being "reduced" (or sometimes with a syllabic consonant as the syllable nucleus rather than a vowel). Various phonological analyses exist for these phenomena.

Lexical stress (word stress) is regarded as being phonemic in English; the position of the stress is generally unpredictable and can serve to distinguish words. For example, the words insight and incite are distinguished in pronunciation only by the fact that the stress is placed on the first syllable in the former word, and on the second syllable in the latter. Similarly, the noun and the verb increase are distinguished by the placement of the stress in the same way – this is an example of an initial-stress-derived noun. Moreover, even within a given letter sequence and a given part of speech, lexical stress may distinguish between different words or between different meanings of the same word (depending on differences in theory about what constitutes a distinct word): For example, initial-stress pronunciations of offense /ˈɒˌfɛns/ and defense /ˈdiːˌfɛns/ denote concepts specific to sports, whereas pronunciations with stress on the words' respective second syllables (offense /ɒˈfɛns/ and defense /dɪˈfɛns/) denote concepts related to the legal (and, for defense, the military) field and encountered in sports only as borrowed from the legal field in the context of adjudicating rule violations.

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