A term used in phonetics to refer to the degree of force used in producing a syllable. The usual distinction is between stressed and unstressed syllables, the former being more prominent than the latter (and marked in transcription with a raised vertical line, [‘].) The prominence is usually due to an increase in loudness of the stressed syllable, but increases in length and often pitch may contribute to the overall impression of prominence. From the viewpoint of phonology, the main function of stress is to provide a means of distinguishing degrees of emphasis or contrast in sentences (sentence stress). In the American structuralist tradition, four such degrees are usually distinguished, and analysed as stress phonemes, namely (from strongest to weakest) (1) ‘primary’, (2)’secondary’, (3)’tertiary’, and (4)’weak’. These contrasts are, however, demonstrable only on words in isolation. Alternative views recognized different kinds and degrees of stress, the simplest postulating a straight stressed v. unstressed contrast. In distinctive feature theories of phonology, the various degrees of stress are assigned to the syllables of words by means of the repeated application of rules (such as ‘lexical’, ‘compound’ and ‘nuclear’ stress rules). Some analysts maintain there is a distinction to be made between linguistic contrast involving loudness and those additionally involving pitch.