What is a natural class?

Definition
	A natural class is a set of sounds that have certain phonetic features in common.
	All the members of a natural class are affected in the same way in the same environment. Similarly, all members of a natural class have the same effect on other sounds that occur in their environment.
	For a group of sounds to constitute a natural class,
	they must all share one or more features and there should be no other sounds in the language that have this feature or combination of features.

Examples (Isthmus Zapotec, Mexico)

Voiced plosives {b, d, g} form a natural class. All the members of the set are affected the same way in the same environment.

For example, following the voiceless S (possessive prefix), voiced plosives are realized as the corresponding voiceless plosives. These voiceless plosives form another natural class {p, t, k}:

bere	‘chicken’	S-pere-be	‘his chicken’
biuuza?	‘guest’	S-piuuza-be	‘his guest’
daa	‘mat’	S-taa-be	‘his mat’
doo	‘rope’	S-too-be	‘his rope’
geta	‘tortilla’	S-keta-be	‘his tortilla’
gamiZa?	‘shirt’	S-kamiZa-be	‘his shirt’

Source:

Merrifield 1987 80

Examples (English)

Voiceless plosives form a natural class. They all have the same effect on voicing a following fricative (realized as [s]). Likewise, voiced plosives form a natural class and all have the same effect on a following fricative (realized as [z]).

map[s]	tab[z]
cup[s]	cub[z]
mat[s]	fad[z]
hit[s]	bid[z]
pack[s]	rag[z]
tick[s]	leg[z]

Source:

Burquest and Payne 1993 10

Kinds
	Here are some kinds of natural classes:
	Plosive Coronal consonant Voiced fricative Voiceless fricative Rounded vowel Sonorant

Context for this page:

Concept module: natural class
In overview module: Glossary (Linguistics): N
In modular book: Glossary of linguistic terms, by Eugene E. Loos (general editor), Susan Anderson (editor), Dwight H., Day, Jr. (editor), Paul C. Jordan (editor), and J. Douglas Wingate (editor)
In bookshelf: Linguistics

This page is an extract from the LinguaLinks Library, Version 5.0 published on CD-ROM by SIL International, 2003. [Ordering information.]

Page content last modified: 5 January 2004