A term used in phonetics and linguistics primarily to refer to any discrete unit that can be identified, either physically or auditorily, in the stream of speech. Segmentation can take place using either physical or auditory criteria: in the former case, acoustic or articulatory change-points can be identified as boundaries of segments; in latter case, perceptible changes in quality or quantity, often showing the influence of the language’s phonemic units, are the basis of division. ‘Segment’ has developed an abstract sense in generative phonology, where it is used for a mental unit of phonological organization - one of a series of minimal units which, however, are not strung together in a simple linear way. In this model, no physical reality is being segmented.