The Atomic Phonology (AP) School deposits that an atomic rule is a universal rule of grammar that incorporates the most restrictive conditions for the rule type in any language. An atomic rule specifies all the necessary conditions from which variants of the rule can be predicted. Its essential claim toward the full set of necessary phonological rules is as follows:
1.
A relatively small finite set of rules (atomic
rules) is highly restrictive and innately available.
2.
Universal principles govern variation in the
form of those rules.
1.
Basic Word-final Devoicing (WFD) Rule: This
rule occurs in many languages, e.g., German, Polish, and Russian.
[-sonorant]
→
[voice] /___# （All
obstruents are voiceless word-finally.）
2.
Variant (Restricted rule): This rule occurs in
languages like Ferrarese Italian,
Turkish, and certain Greek dialects.
[-sonorant,
-continuant] →
[voice] /___#（All
obstruent stops are voiceless word-finally.）
The Atomic Phonology represents one particular approach to the
characterization of what
a possible rule of grammar is.
Atomic
Phonology and Phonological Variation. By William D. Keel.
（Out
of Print）
Asher. 1994. The Encyclopedia of Language and Linguistics.
Dinnsen, Daniel. A. 1979. Atomic phonology. In: Dinnsen D. A. (ed.) Current Approaches
to Phonological Theory. Bloomington, IN:
Indianan UP.