Phonological rule

A phonological rule is a formal way of expressing a systematic phonological or morphophonological process or diachronic sound change in language. Phonological rules are commonly used in generative phonology as a notation to capture sound-related operations and computations the human brain performs when producing or comprehending spoken language. They may use phonetic notation or distinctive features or both. A phonological rule is a formal way of expressing a systematic phonological or morphophonological process or diachronic sound change in language. Phonological rules are commonly used in generative phonology as a notation to capture sound-related operations and computations the human brain performs when producing or comprehending spoken language. They may use phonetic notation or distinctive features or both. John Goldsmith (1995) defines phonological rules as mappings between two different levels of sounds representation—in this case, the abstract or underlying level and the surface level—and Bruce Hayes (2009) describes them as 'generalizations' about the different ways a sound can be pronounced in different environments. That is to say, phonological rules describe how a speaker goes from the abstract representation stored in their brain, to the actual sound they articulate when they speak. In general, phonological rules start with the underlying representation of a sound (the phoneme that is stored in the speaker's mind) and yield the final surface form, or what the speaker actually pronounces. When an underlying form has multiple surface forms, this is often referred to as allophony. For example, the English plural written -s may be pronounced as (in 'cats'), (in 'cabs', 'peas'), or as (in 'buses'); these forms are all theorized to be stored mentally as the same -s, but the surface pronunciations are derived through a phonological rule. In most dialects of American English, speakers have a process known as intervocalic alveolar flapping that changes the consonants /t/ and /d/ into a quick flap consonant ( in words such as 'butter' () and 'notable' (). The stop consonants /t/ and /d/ only become a flap in between two vowels, where the first vowel is stressed and the second is stressless. It is common to represent phonological rules using formal rewrite rules in the most general way possible. Thus, the intervocalic alveolar flapping described above can be formalized as The rule given above for intervocalic alveolar flapping describes what sound is changed, what the sound changes to, and where the change happens (in other words, what the environment is that triggers the change). The illustration below presents the same rule, with each of its parts labelled and described.