In general we can say, that two sounds are “distinctive” if sound differences cause a distinction in meaning. You already came across one way of how to determine whether two sounds in a language are distinctive: identify a minimal pair, which is a pair of words that differ only by a single sound in the same position, and which have different meanings but are otherwise identical.
- (1) bill; dill; gill, rib; rid; rig
- (2) beat; boot, book; beak
- (3) moon vs. good? duty vs. cook? thin vs. that?
When a feature distinguishes one phoneme from another, it is a distinctive feature. This difference also accounts for the difference in meaning. Consider the following minimal pair.
seal vs. zeal: In this example, the distinctive feature [voice] distinguishes [s] from [z]. The two are contrasting phonemes. But the two are neither allophones nor in complementary distribution. The only difference is the distinctive feature [voicing]. We can also group the sounds of a language according to their features.
The term natural classes refers to groups of sounds in a language which share some articulatory or auditory features. For a group of sounds to be a natural class it must include all of the sounds that share a particular feature or group of features; a set of phonemes uniquely defined by a small number of distinctive features such that the set plays a significant role in expressing the phonological regularities; a group of sounds that share one or more distinctive features. One example:
- a. [p,t,k]: form the natural class voiceless stops;
- b. [p,l,w]: do not form a natural class