4.4 Natural Classes
Check Yourself
Video Script
We saw in the last unit that a natural class is a group of speech segments that have some features in common. Because they share features, they also tend to behave similarly to each other in the grammar of a language. We also learned how to use the notation of a feature matrix to describe the features that the members of a natural class have in common. Remember that the more features we list, the smaller the natural class gets, and the fewer features we list, the larger the class we’re describing.
The two largest natural classes can be described with just one feature! All segments that have an obstruction in the vocal tract are [+consonant], and the vowels, which have no obstruction in the vocal tract, are [-consonant]. Notice that the feature consonant is binary, meaning it has exactly two values: plus or minus. This means that we don’t need a separate feature to label the sounds that are vowels: using the binary feature notation we can just say that consonants are [+consonant] and all vowels are [-consonant].
Now, why did I say that most consonants are [+consonant]? Could there be consonants that aren’t totally consonants? Think back to when we first started learning to categorize sounds. Remember we said the glides /j/ and /w/ have very little obstruction in the vocal tract. So even though /j/ and /w/ often behave like consonants, they get labelled as [-consonant] in the feature system. This is how we indicate that also they share some properties with vowels, namely, the property of having the vocal tract unobstructed.
The next feature that groups segments into the major classes has to do with sonority, or acoustic energy. Because of the relatively open vocal tract, all vowels are [+sonorant]. But not all consonants are [-sonorant]. Approximants also have a relatively open vocal tract, so all glides and liquids are also [+sonorant]. And when air circulates through the nasal cavity, that also creates a lot of acoustic energy so all the nasal consonants are also [+sonorant]. All other sounds, that is, stops, fricatives, affricates, and so on, are minus sonorant because they have lower sonority. Informally, we call the non-sonorant class of sounds obstruents, but we don’t need a separate feature label for obstruents because of how the binary feature system works: we just identify them as [-sonorant].
The third major feature groups sounds according to whether they can be the nucleus of a syllable or not. There’s a lot of overlap between sounds that are [+sonorant] and [+syllabic], but the two classes aren’t totally identical. I’m sure you can already guess that all vowels have the feature [+syllabic]. By default, all consonants are [-syllabic], but remember that some consonants can sometimes serve as the nucleus of a syllable — do you remember which ones? The liquids and nasals become [+syllabic] only when they’re the nucleus of a syllable.
These three features are called the major class features bec