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’ |
(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] |