Definition:
Two speech sounds are in complementary distribution when they never occur in the same phonological environment — each appears only where the other doesn’t. Sounds in complementary distribution are typically allophones of the same phoneme rather than separate phonemes. The environments are predictable: given the surrounding sounds, you can always predict which variant will appear.
In-Depth Explanation
Complementary distribution is the key diagnostic for identifying allophones. If two sounds are in complementary distribution, they don’t contrast — they are context-dependent variants of a single underlying phoneme.
Textbook example — Japanese /s/ and /ɕ/:
| Environment | Surface Sound | Example |
|---|---|---|
| Before /a/ | [s] | さ [sa] |
| Before /ɯ/ | [s] | す [sɯ] |
| Before /e/ | [s] | せ [se] |
| Before /o/ | [s] | そ [so] |
| Before /i/ | [ɕ] | し [ɕi] |
[s] and [ɕ] never appear in the same environment — they are in complementary distribution. Therefore, they are allophones of a single phoneme /s/. Japanese speakers don’t perceive them as different sounds; the shift from [s] to [ɕ] before /i/ is automatic and below conscious awareness.
Another Japanese example — /t/, [tɕ], and [ts]:
| Environment | Surface Sound | Example |
|---|---|---|
| Before /a, e, o/ | [t] | た [ta], て [te], と [to] |
| Before /i/ | [tɕ] | ち [tɕi] |
| Before /ɯ/ | [ts] | つ [tsɯ] |
[t], [tɕ], and [ts] are in complementary distribution — allophones of the same phoneme /t/. Japanese speakers don’t hear ち as starting with a different consonant than た; they’re both “t-row” sounds.
The contrasting situation is free variation (two sounds in the same environment with no meaning change) and phonemic contrast (two sounds in the same environment with a meaning change — forming minimal pairs).
For language learners, understanding complementary distribution helps in two ways:
- It explains why native speakers “can’t hear” certain distinctions that seem obvious to you
- It identifies which sound variants are predictable (and therefore don’t need to be memorized separately)
Related Terms
See Also
Research
- O’Grady, W., Dobrovolsky, M., & Katamba, F. (1997). Contemporary Linguistics: An Introduction (3rd ed.). Longman. — Clear textbook presentation of complementary distribution with step-by-step examples.
- Vance, T. J. (2008). The Sounds of Japanese. Cambridge University Press. — Japanese allophonic patterns that exemplify complementary distribution.