Stress and vowel reduction in English

Main article: Vowel reduction

In English, vowel reduction is the centralization and weakening of an unstressed vowel, such as the characteristic change of many vowels at the ends of words to schwa. Stressed vowels are never reduced in English.

Reduced vowels

Vowel reduction is phonemic in English. That is, there are two "tiers" of vowels in English, full and reduced; traditionally many English dictionaries have attempted to mark the distinction by transcribing unstressed full vowels as having "secondary" stress, though recently this has been abandoned in dictionaries such as the Oxford English Dictionary. English has up to five reduced vowels, though this varies with dialect and speaker. Schwa is the most common, and orthographically it may be denoted by any of the vowel letters:

• The a in about.
• The e in synthesis.
• The o in harmony.
• The u in medium.

The following are also schwas, except in dialects that have two distinct reduced vowels (see below).

• The i in decimal.
• The y in syringe.

Whereas the sound represented by the er in water is a schwa in non-rhotic accents like Received Pronunciation, in rhotic dialects like most of North American English, "er" designates an r-colored schwa, [ɚ], which is pronounced like schwa, except the tongue is pulled back in the mouth and "bunched up".

In some dialects of English there is a distinction between two vowel heights of reduced vowels, schwa and "schwi", the near-close central unrounded vowel /ɪ̈/ (or equivalently /ɨ̞/). In the British phonetic tradition, this is written /ɪ/, and in the American tradition /ɨ/. (The OED has recently converted to /ᵻ/ (ɪ).) An example of a minimal pair contrasting schwa and schwi:

• The e in roses is a schwi
• The a in Rosa’s is a schwa

(See Phonological history of English high front vowels.)

Many dialects also retain rounding in reduced vowels, with /uː/ and /ʊ/ reducing to [ʊ̈] (or equivalently /ʉ̞/; /ᵿ/ (ʊ) in OED transcription), as in into /ˈintʊ/, and /oʊ/ reducing to /ɵ/, as in widow /ˈwɪdɵ/. Bolinger (1989) cites a three-way contrast, a mission /əˈmɪʃən/, emission /ɨˈmɪʃən/, and omission /ɵˈmɪʃən/.

The other sounds that can serve as the peak of reduced syllables are the syllabic consonants. The consonants that can be syllabic in English are the nasals /m/, /n/, /ŋ/, and /l/ (actually a dark l). For example:

• The m in prism is sometimes a syllabic /m/.
• The on in prison is a syllabic /n/.
• The word and in the phrase lock and key in more rapid speech is sometimes pronounced as a syllabic /ŋ/.
• The le in cycle and bottle is a syllablic /l/.

These reduced vowels contrast in the word parallelepipedal /ˌpærəlɛlᵻˈpɪpɛdl̩/, and in some dialects idler /ˈaɪdl̩ɚ/.

The vowels and diphthongs /ɔː/, /aʊ/, and /ɔɪ/ are never reduced, and all vowels may occur in unstressed position without reduction, especially in compound words. (These are often transcribed in dictionaries as having secondary stress, but that is a convention for unreduced vowels that occur after the primary stress. See secondary stress.)

Unstressed but unreduced vowels

Vowel	Example	Pronunciation
/iː/	manatee	[ˈmænətTemplate:IPA bold dark red]
/ɪ/	chauvinism	[ˈʃoʊvɨnTemplate:IPA bold dark redzm]
/eɪ/	Monday	[ˈmʌndTemplate:IPA bold dark red]
/ɛ/	enlist	[Template:IPA bold dark rednˈlɪst]
/æ/	valet	[vTemplate:IPA bold dark redˈleɪ]
/ʌ/	unknown	[Template:IPA bold dark rednˈnoʊn]
/ɑː/	grandma	[ˈɡræmTemplate:IPA bold dark red]
/ɒ/	neon	[ˈniːTemplate:IPA bold dark redn]
/ɔː/	outlaw	[ˈaʊtlTemplate:IPA bold dark red]
/oʊ/	limo	[ˈlɪmTemplate:IPA bold dark red]
/ʊ/	fulfill	[fTemplate:IPA bold dark redlˈfɪl]
/uː/	tofu	[ˈtoʊfTemplate:IPA bold dark red]
/aʊ/	discount	[ˈdɪskTemplate:IPA bold dark rednt]
/aɪ/	idea	[Template:IPA bold dark redˈdiːə]
/ɔɪ/	royale	[ɹTemplate:IPA bold dark redˈæl]

Nonetheless, it is true that some vowels, such as /ɪ/ and /ʌ/, reduce quite readily, so that there are not many English words which have them in unstressed positions.

One of the effects of vowel reduction is the partial loss of voicing distinctions in preceding consonants. With a full vowel, as in manatee, an unvoiced consonant is typically aspirated: [ˈmænətʰiː]. However, with a reduced vowel, as in humanity, aspiration is lost and the consonant may even become partially voiced. In American English, in the case of /t/, it may also be flapped: [çjʊˈmænɪ̈ɾi]. (Bolinger 1989:358) According to Wells (1990), in the absence of morpheme boundaries or phonotactical constraints, a consonant between a full and a reduced vowel generally belongs to the syllable with the full vowel, whereas a consonant between two reduced vowels belongs to the first syllable. According to this analysis, manatee is /ˈmæn.ə.tiː/ and humanity is /hjʊ.ˈmæn.ɪt.i/; voiceless plosives are only aspirated at the beginning of syllables, and /t/ can only be flapped at the end of a syllable: compare might I [maɪt.aɪ] → /mʌɪɾaɪ/ and my tie [maɪ.taɪ] → /maɪtʰaɪ/.

Alternation

Main article: Weak form and strong form

Vowel reduction occurs with varying degrees of stability. In some words, an unstressed vowel is never reduced, and in some it is always reduced, but in a large number the extent of reduction depends on how quickly or carefully the speaker enunciates the word. For example, the o in obscene may be pronounced either as full [ɒ] or as reduced [ə], but the historical o sound in gallon is never a full vowel, no matter how carefully one enunciates. (Bolinger 1989:358)

Many English grammatical (function) words alternate between having full but unstressed vowels and reduced vowels, depending on context. For example, the is typically /ðiː/ before a vowel-initial word (the apple) but /ðə/ before a consonant-initial word (the pear), though this distinction is being lost in the United States. Similarly with to: to America /tuː/ vs. to Britain /tə/. Most words, however, alternate depending on how much emphasis they are accorded. When stress shifts to the word, the vowel must be full. Some of these are:

• can: I can go /ˈaɪ kŋ ɡoʊ/, but you can? /juː ˈkæn/
• and: /ænd/, but also you and me /ˌjuː ən ˈmiː/,
• he: He will go /ˈhiː wɨl ɡoʊ/, but also will he go? /ˈwɪl ɪ ɡoʊ/,

and so on with a, at, would, that, has, etc.

There are also a number of English verb-adjective pairs that are distinguished solely by vowel reduction. For example, in some dialects, separate as a verb (as in 'what separates nation from nation') has a full final vowel, /ˈsɛpəreɪt/, whereas the corresponding adjective (as in 'they sleep in separate rooms') has a reduced vowel: /ˈsɛpərət/ or /ˈsɛprət/.

See also

• Schwa
• Tenseness
• Vowel reduction
• Vowel reduction in Russian