Stress (linguistics)
In linguistics, and particularly phonology, stress or accent is the 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. 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 lexical stress, where the position of stress in a word is not predictable in that way but lexically encoded. Sometimes more than one level of stress, such as primary stress and secondary stress, may be identified.
Stress is not necessarily a feature of all languages: some, such as French and Mandarin Chinese, 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 they depend to some extent on which language is being spoken. Stressed syllables are often louder than non-stressed syllables, and they 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, and 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 is minimal between the acoustic signals of stressed and those of unstressed syllables.Those 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. They can be compared to the various types of accents in music theory. In some contexts, the term stress or stress accent specifically means 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, and 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 that are realized with a relatively large swing in fundamental frequency, and unstressed syllables typically have smaller swings.
Stressed syllables are often perceived as being more forceful than non-stressed syllables.
Word stress
Word stress, or sometimes lexical stress, is the stress placed on a given syllable in a word. The position of word 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, for example in English. 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, Hungarian and Latvian, 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 weight 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, which 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 Mandarin Chinese. French and Georgian can be considered to have no real lexical stress.
Phonemic stress
With some exceptions above, languages such as Germanic languages, Romance languages, the East and South Slavic languages, Lithuanian, Greek, as well as others, such as Northwest Caucasian and Turkic languages, in which the position of stress in a word is not fully predictable, are said to have phonemic stress. Stress in these languages is usually truly lexical and must be memorized as part of the pronunciation of an individual word. In some languages, such as Spanish, Portuguese, Catalan, 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 wikt:Tenor#German ; and Italian wikt:ancora#Italian.
In many languages with lexical stress, it is [|connected with alternations in vowels and/or consonants], which means that vowel quality differs by whether vowels are stressed or unstressed. There may also be limitations on certain phonemes in the language in which stress determines whether they are allowed to occur in a particular syllable or not. That is the case with most examples in English and occurs systematically in Russian, such as за́мок vs. замо́к ; and in Portuguese, such as the triplet sábia, sabia, sabiá.
Dialects of the same language may have different stress placement. For instance, the English word laboratory is stressed on the second syllable in British English, 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. Even the exceptions, such as mankínd, are instead often stressed on the first component by some people or in some kinds of English. The same components as those of a compound word are sometimes used in a descriptive phrase with a different meaning and with stress on one or both words, but that descriptive phrase is then not usually considered a compound. Examples include bláck bírd versus bláckbird, táilbone versus táil bóne, and páper bág versus páper bag versus páperbag.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 prosody is recognized and unstressed syllables are phonemically distinguished for vowel reduction. They find that the multiple levels posited for English, whether primary–secondary or primary–secondary–tertiary, are not phonetic stress, and that the supposed secondary/tertiary stress is not characterized by the increase in respiratory activity associated with primary/secondary stress in English and other languages.