What is the definition of "complementary distribution"?

Question

Allophones are defined by means of complementary distribution. As I understand it, a complementary distribution is a "mutually exclusive" relationship between two phones, with regard to a certain phonetic environment. That is, one of the phones will only be found in that environment (and nowhere else) while the other phone will never be found in that environment (but will be found somewhere else).

For example, In English, [pʰ] and [p] are allophones of the phoneme /p/, since [pʰ] can be found at the beginning of syllables ([pʰɪn]) and nowhere else. Likewise, [p] is never found at the beginning of syllables, but can be found in other positions ([spɪn]). Summarizing in a table:

Now, in Brazilian Portuguese, [w] and [l] are considered allophones of /l/. The reasoning is similar: [l] is never found at the end of syllables, but can be found in other places ([a.'kli.vi], "slope"). [w], on the other hand, is found at the end of syllables ([saw], "salt"). The problem is: [w] can also be found elsewhere ([a.'kwi;.fe.ru], "aquifer"). The table for this distribution, therefore, would be like this:

This means that, in some environments both [w] and [l] can be found, as in the [a.'kli.vi] versus [a'.kwi.fe.ru] example. So, evidently, I'm failing to understand what "complementary distribution" really is. Any help to clarify the concept would be much appreciated!

Answer 1

I think you need to tease apart the concept of allophony from the concept of complementary distribution. As people have mentioned in the comments, the two don't necessarily go hand in hand--i.e. it is not necessarily the case that two phones that are in complementary distribution can be assumed to be allophones of the same phoneme (as Alex B. mentioned), nor is it the case that the distribution of two phones--each of which is a possible realization of a single phoneme--will never overlap in their distribution. It's the second assertion that is relevant for your Brazilian Portuguese example.

The "trick" is that sometimes different phonemes can have allophones "in common", i.e. Phoneme A might sometimes be realized as Phone Y, but Phoneme B might also sometimes be realized as Phone Y:

/A/ --> [X] in some environment, [Y] in some other environment

/B/ --> [Y] in some environment, [Z] in some other environment

This happens a lot in neutralizations and mergers. In languages with word-final devoicing, for example, maybe /d/ is realized as [t] word-finally but as [d] elsewhere. But /t/ would also be realized as [t] word-finally. If one encounters a [t] at the end of a word, one cannot be sure without additional information whether it is a realization of /t/ or /d/.

In your example, [w] is probably an allophone of some phoneme that can sometimes be realized as [w] and sometimes [l] (in some sense the "naming" of phonemes is arbitrary, but I'd probably call it /l/ since that seems to be the clear "elsewhere" realization) and [w] is probably also an allophone of a different phoneme (one that I would call /w/).

Now, it is true that allophones of the same phoneme must be in complementary distribution, but the two [w]s and the [l] in your table are not actually all realizations of the same phoneme. So, here is a revised assessment of their distribution, taking their underlying forms into account:

[l] (from /l/) not found at the end of a syllable, but found elsewhere

[w] (from /l/) found at the end of a syllable, but not found elsewhere

[w] (from /w/) found elsewhere (and perhaps also at the end of a syllable?)

So, the [l] and the first [w] are in fact in complementary distribution. I hope that makes sense!

Answer 2

complementary distribution mean that the allophones of a particular phoneme occur in different phonetic environment , the phonetic environment determines which of the allophones is used in pronouncing a word . For example ,the two allophones of the phoneme /p/, namely , [pH] and [p-]are in complementary distribution the first occurs at the end of the word,as in Pat and Pot, the second may occur at the end of the ward , as in help. the fact of their complementary distribution means that these allophones do not occur in minimal pairs in English.