Phonological rules are a system of writing, using formal notation, which allows linguists to express how to pronounce speech phonetically. Phonological rules are part of every speaker's linguistic competence (Finch 2000, p. 64). As well, these rules operate unconsciously (Finch 2000, p. 64). That is, we don't actually realize that we are following phonological rules when we speak and no one teaches us these rules. When we speak, we are undoubtedly following various phonological rules without actually knowing we are doing so. Phonological rules take on the following form (Finegan and Besinger 1989, p. 70);
A "" B / C --- D
This can be read as A becomes B in the environment following C and preceding D. The left side of the arrow, the A, indicates what sounds are impacted by the rule in question. The right side of the technical notation indicates that change that takes place under that particular environment. The "" can be read as "becomes" to show that the the symbol on the left becomes whatever is on the right of the arrow. The notation / is read to mean "in the environment of" (Fromkin & Rodman 1993, p. 243).
Every language has its own phonological rules. Three examples of phonological rules in English and one example of a phonological rule in Japanese will be used to illustrate how phonological rules are used. These phonological rules include, the rules of aspiration, nasalization and the devoicing of Japanese high vowels /i/ and /u/.
First, the aspiration rule affects the phonemes /p/, /t/ and /k/. When these occur at the beginning of a stressed syllable, they are produced with a small puff of air. So, the rule for aspiration can be stated as follows:
Voiceless plosives are...