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In linguistics, stress is the relative emphasis that may be given to certain syllables in a word, or to certain words in a phrase or sentence. Stress is typically signaled by such properties as increased loudness and vowel length, full articulation of the vowel, and changes in pitch. The terms ''stress'' and ''accent'' are often used synonymously, but they are sometimes distinguished, with certain specific kinds of prominence (such as pitch accent, variously defined) being considered to fall under accent but not under stress. In this case, stress specifically may be called stress accent or dynamic accent. 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 first or the penultimate. Other languages, like English, 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 are considered to lack lexical stress entirely. The stress placed on words within sentences is called sentence stress or prosodic stress. This is one of the three components of prosody, along with rhythm and intonation. It includes phrasal stress (the default emphasis of certain words within phrases or clauses), and contrastive stress (used to highlight an item − a word, or occasionally just part of a word − that is given particular focus). == 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 (or "neutral") 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 (although this term usually has more specialized meanings), ''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 (or as an antonym to ''pitch accent'' in its various meanings). In Mandarin Chinese, which is a tone 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.〔Kochanski, G., Shih, C., Jing, H.; Quantitative Measurement of Prosodic Strength in Mandarin, Speech Communication 41(4), November 2003, 〕 (See also Stress in Standard Chinese.) Stressed syllables are often perceived as being more forceful than non-stressed syllables. Research has shown, however, that although dynamic accent is accompanied by greater respiratory force, it does not mean a more forceful articulation in the vocal tract. (Much literature emphasizes the importance of pitch changes and pitch motions on stressed syllables, but experimental support for this idea is weak. Nevertheless, most experiments do not directly address the pitch of speech, which is a subjective perceived quantity. Experiments typically measure the speech fundamental frequency, which is objectively measurable, and strongly correlated with pitch, but not quite the same thing.) 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Stress (linguistics)」の詳細全文を読む スポンサード リンク
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