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 contradictory phonological analyses exist for these phenomena.
For example, in the following sentence, a speaker would typically pronounce have with a schwa, as or :
Alice and Bob have arrived.
But in other contexts where the word carries stress, it would be pronounced in its "strong" (unreduced) form as . For example:
Have Alice and Bob arrived? [In response to the question "Have Alice and Bob arrived?"] They have.
Lexical and prosodic stress Lexical stress (word stress) is regarded as 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 syllable being stressed. In insight, the stress is placed on the first syllable; and in incite, on the second. 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 and defense in American English denote concepts specific to sports, whereas pronunciations with stress on the words' respective second syllables (offense and defense ) denote concepts fundamentally 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. British English stresses the second syllable in both sports and legal use.
Some words are shown in dictionaries as having two levels of stress: primary and secondary. For example, the RP pronunciation of organization may be given as , with primary stress on the fourth syllable, secondary stress on the first syllable, and the remaining syllables unstressed. For different ways of analysing levels of stress in English, see below.
English also has relatively strong prosodic stress—particular words within a phrase or sentence receive additional stress to emphasize the information they convey. There is also said to be a natural "tonic stress" that falls on the last stressed syllable of a prosodic unit – for more on this, see below under .
English is classified as a stress-timed language, which means that there is a tendency to speak so that the stressed syllables come at roughly equal intervals. See .
Reduced vowels Certain vowel sounds in English are associated strongly with absence of stress: they occur practically exclusively in unstressed syllables, and conversely, most (though not all) unstressed syllables contain one of these sounds. These are known as reduced vowels, and tend to be characterized by such features as shortness, laxness and central position. (An alternative term is weak vowels.) The exact set of reduced vowels depends on dialect and speaker; the principal ones are described in the sections below.
Schwa and r-coloured schwa Schwa, , is the most common reduced vowel in English. It may be represented in spelling by any of the vowel letters, such as the a in about, the o in harmony, the u in medium, the e in synthesis, the i in decimal or the y in analysis (although the last three are pronounced instead as a near-close vowel by some speakers – see the following section).
In many rhotic dialects, an r-colored schwa, , occurs in words such as water and standard. The r-colored schwa can be analyzed phonemically as .
Reduced vowels in the close unrounded area
In some dialects of English there is a distinction between two vowel heights of reduced vowels: in addition to schwa, there is a distinct near-close central unrounded vowel (or equivalently ). In the British phonetic tradition, the latter vowel is represented with the symbol , and in the American tradition . An example of a minimal pair contrasting these two reduced vowels is Rosas vs. roses: the a in Rosa's is a schwa, while the e in roses (for speakers who make the distinction) is the near-close vowel. See weak vowel merger.
Like schwa, does not correspond in spelling to any single vowel letter. It can be represented by a (for example, message , climate , orange ), e (puppet), i (limit), u (minute), or y (polyp).
Among speakers who make this distinction, the distributions of schwa and are quite variable, and in many cases the two are in free variation: the i in decimal, for example, may be pronounced with either sound. A symbolization convention recently introduced by Oxford University Press for some of their English dictionaries uses the non-IPA "compound" symbol () in words that may be pronounced anywhere between or (including and ); for example, the word noted is transcribed . This indeterminate vowel is sometimes called schwi.
The final vowel of words like happy and coffee is an unstressed front close unrounded vowel most commonly represented with , although some dialects (including more traditional Received Pronunciation) may have . This used to be identified with the phoneme , as in . See happy tensing. However, some contemporary accounts regard it as a symbol representing a close front vowel that is neither the vowel of nor that of ; it occurs in contexts where the contrast between these vowels is neutralized; these contexts include unstressed prevocalic position within the word, such as react . For some speakers, however, there is a contrast between this vowel and in such pairs as taxis vs. taxes and studied vs. studded. See English phonology: § Unstressed syllables under § Vowels.
Reduced vowels in the close rounded area
According to , there is a reduced rounded phoneme as in willow or omission , thus forming a three-way contrast with Willa and Willie or with a mission and emission . This phoneme alternates with the goat vowel .
Analogously to the symbol mentioned above, Oxford University Press have devised the non-IPA symbol to represent a vowel that may be anywhere between and (including and ) in free variation; for example, awful may be pronounced or . Phonologically, this vowel is an archiphoneme representing the neutralization of and . This indeterminate vowel is sometimes called schwu.
A rounded vowel , corresponding to the happY vowel, is widely used in British works for words such as influence , into . Phonologically, this vowel is an archiphoneme representing the neutralization of and .
Syllabic consonants The other sounds that can serve as the peaks of reduced syllables are the syllabic consonants, which can result in syllables with no vowel sound. Alternative pronunciations of syllabic consonants are however also possible. For example, cycle may be pronounced as either with only a dark l sound or as with a schwa followed by the dark l sound.
In other words, a syllabic consonant can be phonologically analyzed as consisting of either just the consonant or of an underlying schwa followed by the consonant. The consonants that can be syllabic in English are principally , , and , for example in cycle (spelled by L followed by a silent e), prism, and prison. In rhotic accents, and are also pronounced as syllabic or .
Unstressed full vowels All full (unreduced; also called strong) vowels may occur in unstressed position (except under theoretical approaches that routinely assign secondary or tertiary stress to syllables containing such vowels – see below). Some examples of words with unstressed syllables that are often pronounced with full vowels in Received Pronunciation are given below (pronunciation may be different in other varieties of English). Unreduced short vowels: in the final syllable of document when used as a verb (compare the heard when the word is used as a noun); in the first syllable of ambition; in the second syllable of neon; in words with the negative prefix un-, such as unknown (compare in until). Long vowels: in the final syllable of grandma; in the final syllable of outlaw; in tofu; in the noun convert; in manatee. Note that this last may stand in contrast to the happY vowel found at the end of humanity. This contrast is further described under below. Diphthongs: in Monday; in piano; in discount; in idea; in royale.
Many other full unstressed vowels also derive historically from stressed vowels, due to shifts of stress over time, such as stress shifting away from the final syllable of French loan words, like ballet and bureau, in British English though not American English, or the loss or change of stress in compound phrases (as in óverseas vóyage from overséas plus vóyage). There is a tendency, though, for such vowels to become reduced over time, especially in very common words.
With vowels represented as and , it may be hard to ascertain whether they represent a full vowel or a reduced vowel. A word that illustrates this challenge is chauvinism, where the first i is either the reduced vowel or the unreduced , while the second is definitively the unreduced .
Compound words Full vowels are commonly, but not always, preserved in unstressed syllables in compound words, such as in bedsheet, moonlit, tentpeg, snowman, and kettledrum.John Wells, "strong and weak", in John Wells's phonetic blog, 25 March 2011 However, in some compounds that are used fairly frequently and therefore more familiarly, the vowel of the unstressed part may be reduced in contrast to compounds that are not: thus, postman but snowman ; England but Thailand ; cupboard but blackboard .
Degrees of lexical stress
Descriptions with primary and secondary stress In many phonological approaches, and in many dictionaries, English is represented as having two levels of stress: primary and secondary. In every lexical word, and in some grammatical words, one syllable is identified as having primary stress, though in monosyllables the stress is not generally marked. In addition, longer words may have one or more syllables identified as having secondary stress. Syllables that have neither primary nor secondary stress are called unstressed.
In International Phonetic Alphabet transcriptions, primary stress is denoted with and secondary stress with . IPA stress marks are placed before the stressed syllable. When citing words in English spelling, primary stress is sometimes denoted with an acute accent and secondary stress with a grave accent , placed over the vowel of the stressed syllable.
Secondary stress is frequently indicated in the following cases: