There are two classes of postalveolar plosives in Kinyarwanda: velars and palatals. In (1) are examples of the velars, and in (2) are examples of the palatals.
(1) Velars [k, g]
|mukuru||[mukuɾúʰ]||"old (Class 1)"|
(2) Palatals [c,ɟ]
|gukenyera||[gucéɲeɾaʰ]||"to tie clothes around the waist"|
There is no contrast between the velars and the palatals. There are, for example, no minimal pairs of different words where one has a velar stop and the other is identical except that it has a palatal stop.
A velar stop occurs only before a back vowel, such as [a], [o], or [u], or before the labiovelar glide [w]. A palatal stop, on the other hand, occurs only before a front vowel, such as [e] or [i]. A stop only occurs in Kinyarwanda before a vowel or a glide, so this exhausts the possible contexts.
The contexts in which velars occur do not overlap with the contexts in which palatals occur (with one systematic exception to be dealt with below:
This is a complementary distribution. Two classes of sounds are in complementary distribution if one class occurs only in a particular context, and the other class occurs only elsewhere. The class that only occurs in one particular context can be refered to as the restricted class. In this example, the restricted class is the set of palatal stops, which occur only in the context before a front vowel. The other class, which occurs only elsewhere, can be called the default class. In the Kinyarwanda case, the default class is the set of velar stops. Another example of complementary distribution is the pattern of palatalization in Turkish.
Morphemes in Kinyarwanda that end in a postalveolar stop have different pronunciations depending on whether a front vowel or a back vowel follows. Two different pronunciations of the same morpheme are called morpheme alternants, and the relation between them is an alternation. All items in the following table begin with ku- and end in -a, and all of them are infinitives. The morphemes ku and a together mark the infinitive. The suffix marking the causative is -i:ʃ or -e:ʃ, according to a pattern of alternation to be discussed in the next section. The applicative suffix is -ir- ~ -er- alternating according to the same pattern. The remaining material, between the prefix ku and the suffixes, is the root with the meaning indicated in the basic verb gloss.
|Basic form (to Verb)||Causative (to make someone Verb)||Applicative (to Verb for someone)||Basic Verb gloss|
In the first row of data, the verb root meaning "smell" is [nu:k] when it is followed by a back vowel (as in the first column) and [nu:c] when it is followed by a front vowel (as in the second and third columns). We indicate that these are two alternants belonging to the same morpheme with a tilde between them: nu:k ~ nu:c. The other root alternations in the table are as follows:
|• ɾek ~ ɾec||"stop"|
|• ɾog ~ ɾoɟ||"bewitch"|
|• manik ~ manic||"hang"|
|• za:mu:k ~ za:mu:c||"climb"|
All these pairs of alternants are distinguished by one alternant having k where the other has c. These alternating sounds are also called alternants, and the relation between them is called alternation and is indicated with a tilde: k ~ c.
When two sounds are alternating, we know that there is a restriction on their distribution relative to each other. There is some context where one of the sounds can occur and the other cannot. In this case, the restriction is the complementary distribution stated above. The alternation is an effect of this generalization about the distribution of sounds.
Alternations are thus very informative, since finding a pattern of alternation points to a restriction on distribution. Phonologists investigating a previously undescribed language seek out alternations, since this is an efficient way to find patterns of distribution.
This particular pattern of distribution, requiring that a consonant in a particular environment be palatal (or alveopalatal) is called palatalization. Palatalization is very common in the world's languages, especially before front vowels (Bhat 1978). Such patterns arise diachronically from the coarticulatory effect of a vowel on a neighboring consonant (Guion 1998). In English, for example, a velar stop before a front vowel is made with a more front closure than a velar stop before a back vowel. This coarticulation pattern is gradient in that the effect of the vowel on the preceding consonant is greater in the parts of that consonant that are closer to that vowel (Butcher and Weiher 1976, Zsiga 1995). In Kinyarwanda, on the other hand, the palatal stop is palatal from beginning to end. The Kinyarwanda pattern appears to be a phonological pattern - a restriction on the distribution of sound categories. Another example of phonological palatalization is in Turkish.
Bhat, D. (1978). A general study of palatalization. In J. Greenberg (ed.) Universals of Human Language, Volume 2: Phonology. Stanford University Press, Stanford, 47-92.
Butcher, A. and E. Weiher (1976). An electropalatographic investigation of coarticulation in VCV sequences. Journal of Phonetics 4. 59-74.
Guion, Susan (1998). The role of perception in the sound change of velar palatalization.Phonetica 55, 18-52.
Zsiga, E. (1995). An acoustic and electropalatographic study of lexical and postlexical palatalization in American English. In B. Connell and A. Arvaniti (eds.) Phonology and Phonetic Evidence: Papers in Laboratory Phonology IV. Cambridge University Press, Cambridge. 282-302.