Stress (linguistics)


In linguistics, and particularly phonology, stress or accent is relative emphasis or prominence given to a certain syllable in a word, or to a certain word in a phrase or sentence. That emphasis is typically caused by such properties as increased loudness and vowel length, full articulation of the vowel, and changes in tone. The terms stress and accent are often used synonymously in that context but are sometimes distinguished. For example, when emphasis is produced through pitch alone, it is called pitch accent, and when produced through length alone, it is called quantitative accent. When caused by a combination of various intensified properties, it is called stress accent or dynamic accent; English uses what is called variable stress accent.
Since stress can be realised through a wide range of phonetic properties, such as loudness, vowel length, and pitch, it is difficult to define stress solely phonetically.
The stress placed on syllables within words is called word stress or lexical stress. Some languages have fixed stress, meaning that the stress on virtually any multisyllable word falls on a particular syllable, such as the penultimate or the first. Other languages, like English and Russian, have variable stress, where the position of stress in a word is not predictable in that way. Sometimes more than one level of stress, such as primary stress and secondary stress, may be identified. However, some languages, such as French and Mandarin, are sometimes analyzed as lacking lexical stress entirely.
The stress placed on words within sentences is called sentence stress or prosodic stress. That is one of the three components of prosody, along with rhythm and intonation. It includes phrasal stress, and contrastive stress.

Phonetic realization

There are various ways in which stress manifests itself in the speech stream, and these depend to some extent on which language is being spoken. Stressed syllables are often louder than non-stressed syllables, and may have a higher or lower pitch. They may also sometimes be pronounced longer. There are sometimes differences in place or manner of articulation – in particular, vowels in unstressed syllables may have a more central articulation, while those in stressed syllables have a more peripheral articulation. Stress may be realized to varying degrees on different words in a sentence; sometimes the difference between the acoustic signals of stressed and unstressed syllables are minimal.
These particular distinguishing features of stress, or types of prominence in which particular features are dominant, are sometimes referred to as particular types of accent – dynamic accent in the case of loudness, pitch accent in the case of pitch, quantitative accent in the case of length, and qualitative accent in the case of differences in articulation. These can be compared to the various types of accent in music theory. In some contexts, the term stress or stress accent is used to mean specifically dynamic accent.
A prominent syllable or word is said to be accented or tonic; the latter term does not imply that it carries phonemic tone. Other syllables or words are said to be unaccented or atonic. Syllables are frequently said to be in pretonic or post-tonic position; certain phonological rules apply specifically to such positions. For instance, in American English, /t/ and /d/ are flapped in post-tonic position.
In Mandarin Chinese, which is a tonal language, stressed syllables have been found to have tones realized with a relatively large swing in fundamental frequency, while unstressed syllables typically have smaller swings.
Stressed syllables are often perceived as being more forceful than non-stressed syllables.

Lexical stress

Lexical stress, or word stress, is the stress placed on a given syllable in a word. The position of lexical stress in a word may depend on certain general rules applicable in the language or dialect in question, but in other languages, it must be learned for each word, as it is largely unpredictable. In some cases, classes of words in a language differ in their stress properties; for example, loanwords into a language with fixed stress may preserve stress placement from the source language, or the special pattern for Turkish placenames.

Non-phonemic stress

In some languages, the placement of stress can be determined by rules. It is thus not a phonemic property of the word, because it can always be predicted by applying the rules.
Languages in which the position of the stress can usually be predicted by a simple rule are said to have fixed stress. For example, in Czech, Finnish, Icelandic and Hungarian, the stress almost always comes on the first syllable of a word. In Armenian the stress is on the last syllable of a word. In Quechua, Esperanto, and Polish, the stress is almost always on the penult. In Macedonian, it is on the antepenult.
Other languages have stress placed on different syllables but in a predictable way, as in Classical Arabic and Latin, where stress is conditioned by the structure of particular syllables. They are said to have a regular stress rule.
Statements about the position of stress are sometimes affected by the fact that when a word is spoken in isolation, prosodic factors come into play, which do not apply when the word is spoken normally within a sentence. French words are sometimes said to be stressed on the final syllable, but that can be attributed to the prosodic stress that is placed on the last syllable of any string of words in that language. Thus, it is on the last syllable of a word analyzed in isolation. The situation is similar in Standard Chinese. French can be considered to have no real lexical stress.

Phonemic stress

Languages in which the position of stress in a word is not fully predictable are said to have phonemic stress. For example, English, Russian, Italian, Portuguese and Spanish. Stress is usually truly lexical and must be memorized as part of the pronunciation of an individual word. In some languages, such as Spanish, Portuguese, Lakota and, to some extent, Italian, stress is even represented in writing using diacritical marks, for example in the Spanish words célebre and celebré. Sometimes, stress is fixed for all forms of a particular word, or it can fall on different syllables in different inflections of the same word.
In such languages with phonemic stress, the position of stress can serve to distinguish otherwise identical words. For example, the English words insight and incite are distinguished in pronunciation only by the fact that the stress falls on the first syllable in the former and on the second syllable in the latter. Examples from other languages include German , but the first syllable in American English, with a secondary stress on the "tor' syllable. The Spanish word video'' is stressed on the first syllable in Spain but on the second syllable in the Americas. The Portuguese words for Madagascar and the continent Oceania are stressed on the third syllable in European Portuguese, but on the fourth syllable in Brazilian Portuguese.

Compounds

With very few exceptions, English compound words are stressed on their first component. And even such exceptions, for example mankínd, are instead often stressed on the first component by some people or in some kinds of English. Sometimes the same components as those of a compound word are used in a descriptive phrase with a different meaning and with stress on both words, but that descriptive phrase is then not usually considered a compound: bláck bírd and bláckbird and páper bág and páper bag.

Levels of stress

Some languages are described as having both primary stress and secondary stress. A syllable with secondary stress is stressed relative to unstressed syllables but not as strongly as a syllable with primary stress. As with primary stress, the position of secondary stress may be more or less predictable depending on language. In English, it is not fully predictable, but the different secondary stress of the words organization and accumulation is predictable due to the same stress of the verbs órganize and accúmulate. In some analyses, for example the one found in Chomsky and Halle's The Sound Pattern of English, English has been described as having four levels of stress: primary, secondary, tertiary, and quaternary, but the treatments often disagree with one another.
Peter Ladefoged and other phoneticians have noted that it is possible to describe English with only one degree of stress, as long as unstressed syllables are phonemically distinguished for vowel reduction. They believe that the multiple levels posited for English, whether primary–secondary or primary–secondary–tertiary, are mere phonetic detail and not true phonemic stress, and often, the alleged secondary stress is not characterized by the increase in respiratory activity normally associated with primary stress in English or with all stress in other languages.

Prosodic stress

Prosodic stress, or sentence stress, refers to stress patterns that apply at a higher level than the individual word – namely within a prosodic unit. It may involve a certain natural stress pattern characteristic of a given language, but may also involve the placing of emphasis on particular words because of their relative importance.
An example of a natural prosodic stress pattern is that described for French above; stress is placed on the final syllable of a string of words. A similar pattern has been claimed for English : the traditional distinction between primary and secondary stress is replaced partly by a prosodic rule stating that the final stressed syllable in a phrase is given additional stress.
Another type of prosodic stress pattern is quantity sensitivity – in some languages additional stress tends to be placed on syllables that are longer.
Prosodic stress is also often used pragmatically to emphasize particular words or the ideas associated with them. Doing this can change or clarify the meaning of a sentence; for example:
As in the examples above, stress is normally transcribed as italics in printed text or underlining in handwriting.
In English, stress is most dramatically realized on focused or accented words. For instance, consider the dialogue
In it, the stress-related acoustic differences between the syllables of "tomorrow" would be small compared to the differences between the syllables of "dinner", the emphasized word. In these emphasized words, stressed syllables such as "din" in "dinner" are louder and longer. They may also have a different fundamental frequency, or other properties.
The main stress within a sentence, often found on the last stressed word, is called the nuclear stress.

Stress and vowel reduction

In many languages, such as Russian and English, vowel reduction may occur when a vowel changes from a stressed to an unstressed position. In English, unstressed vowels may reduce to schwa-like vowels, though the details vary with dialect. The effect may be dependent on lexical stress, or on prosodic stress.
Many other languages, such as Finnish and the mainstream dialects of Spanish, do not have unstressed vowel reduction; in these languages vowels in unstressed syllables have nearly the same quality as those in stressed syllables.

Stress and rhythm

Some languages, such as English, are said to be stress-timed languages; that is, stressed syllables appear at a roughly constant rate and non-stressed syllables are shortened to accommodate that, which contrasts with languages that have syllable timing or mora timing, whose syllables or moras are spoken at a roughly constant rate regardless of stress. For details, see Isochrony.

Historical effects

It is common for stressed and unstressed syllables to behave differently as a language evolves. For example, in the Romance languages, the original Latin short vowels and have often become diphthongs when stressed. Since stress takes part in verb conjugation, that has produced verbs with vowel alternation in the Romance languages. For example, the Spanish verb volver has the form volví in the past tense but vuelvo in the present tense. Italian shows the same phenomenon but with alternating with instead. That behavior is not confined to verbs; note for example Spanish viento "wind" from Latin ventum, or Italian fuoco "fire" from Latin focum.

Stress "deafness"

An operational definition of word stress may be provided by the stress "deafness" paradigm. The idea is that if listeners perform poorly on reproducing the presentation order of series of stimuli that minimally differ in the position of phonetic prominence, the language doesn't have word stress. The task involves a reproduction of the order of stimuli as a sequence of key strokes, whereby key "1" is associated with one stress location and key "2" with the other. A trial may be from 2 to 6 stimuli in length. Thus, the order is to be reproduced as "1121". It was found that listeners whose native language was French performed significantly worse than Spanish listeners in reproducing the stress patterns by key strokes. The explanation is that Spanish has lexically contrastive stress, as evidenced by the minimal pairs like tópo and topó, while in French, stress does not convey lexical information and there is no equivalent of stress minimal pairs as in Spanish.
An important case of stress "deafness" relates to Persian. The language has generally been described as having contrastive word stress or accent as evidenced by numerous stem and stem-clitic minimal pairs such as /mɒhi/ and /mɒh-i/ . The authors argue that the reason that Persian listeners are stress "deaf" is that their accent locations arise postlexically. Persian thus lacks stress in the strict sense.

Spelling and notation for stress

The orthographies of some languages include devices for indicating the position of lexical stress. Some examples are listed below:
Though not part of normal orthography, a number of devices exist that are used by linguists and others to indicate the position of stress when it is desirable to do so. Some of these are listed here.