Contrastive distribution is a relationship between two different elements in phonology, in which the substitution of a component with another leads to changes in semantic meaning. In other words, if two sounds in a language in the same contexts produce different meanings, it is a contrastive distribution. For instance, the English language has two oral alveolar consonants [t] and [d].
These sounds are in contrastive distribution since replacing one of them with another leads to changes in meanings. The relationship can be seen in the pair [taɪd] and [daɪd], which produce two words, tide and died, with different lexical meanings. The contrastive distribution also helps to distinguish between phonemes and allophone, or variations of phonemes.
This is vital for non-native speakers because some phonemes may not be present in their first language. For instance, a native English speaker will have no problem distinguishing between [ð] and [d] and stating that these are phonemes. However, a foreigner may need to compare [briːð] and [bri:d] to understand that these are two different sounds.
However, two elements may not have a differentiating function, which means that two sounds may be in non-contrastive relationships. For instance, American English [dæns] and British English [da: ns] are variations in the pronunciation of the word dance. These two sounds in this context are considered to be in free variation, which means that the substitution of one element with another does not lead to changes in semantics (Complementary distribution and free variation no date).
In this situation, the sounds are considered to be allophones, which are variations in pronunciation. Such a relationship is often met in dialects of one language, which implies that changes in pronunciation do not change the meaning of words. In order to appreciate the difference between contrast distribution and free variation, it is beneficial to consider additional examples. In the word pair [dɛn] and [ɹɛn], the sounds [d] and [ɹ] are in contrastive distribution. If one substitute [d] for [ɹ], the word den will be replaced with the word wren.
Since the substitution causes a change in meaning, these two sounds should be considered phonemes. Similar logic can be used to the word pair [fæt] and [væt]. The substitution of [f] with [v] in the word fat will lead to the creation of a new word VAT, which is an abbreviation for value-added tax. Therefore, these two sounds are believed to be in contrastive distribution. In contrast, sounds [t] and [ʔ] in [ˈpati] and [ˈpaʔi] are allophones, and substitution of one with another will not produce a new word.
Therefore, the sounds are believed to be in free variation, representing the differences in pronunciation of one word. While differences in free variation and contrasting distribution seem straightforward, it is not always the case. Distinguishing between the two phenomena discussed may be a challenge in narrow situations.
When considering sounds [f] and [θ] in [θɪŋk] and [f], they seem to represent different phonemes. The substitution of [f] in the word think will create a new word fink. However, considering the phenomenon of th-fronting, which is pronouncing phonemes /θ/ and /ð/ as [f] and [v], the matter is unclear. Clark and Trousdale (2010) claim that [f] and [θ] can be in a free variation relationship in some dialects, such as the Central Scottish one. Therefore, the relationships of the sounds in pair [θɪŋk] and [fɪŋk] is a matter of dispute.
When considering the relationships between elements in phonology, it is also vital to understand complementary distribution. The term means that where one sound of the pair occurs, the other cannot do so (Complementary distribution and free variation no date). For instance, in the words top, pill, kill, and till sounds [pʰ], [kʰ], and [tʰ] are aspirated. However, in words, stop, spill, skill, and still, the sounds [p], [k], and [t] are not aspirated. In these three pairs of words, if a plosive consonant, such as
, , or , stands at the beginning of the word and is followed by a stressed vowel, it will be aspirated, while if it is preceded by a consonant, it will be unaspirated.
Aspirated and unaspirated allophones are excellent examples of complementary substitutions. The word complementary means that the context in which the allophones of a phoneme appear can never be the same (Complementary distribution and free variation no date). The three types of relationships between two elements in phonology discussed above demonstrate a vital difference between phonemes and allophones. The occurrence of allophones is predictable, while the occurrence of phonemes is unpredictable.
One can safely say that at the beginning of the word
will be aspirated if it is followed by a stressed vowel. However, the context cannot predict what phoneme will be used because the ability to be contrasted in one context is one of the fundamental characteristics of phonemes.