As we saw in Chapter 2, the class of consonants can be divided into a number of sub-groupings on the basis of their manner of articulation. The ﬁrst division we will consider here is obstruent vs. sonorant. For obstruents, the airﬂow is noticeably restricted, with the articulators either in complete closure or close approximation. For sonorants, either there is no such restriction in the oral tract, or the nasal tract is open; either way, the air has free passage through the vocal tract. The class of obstruents can be further subdivided into stops, fricatives and affricates, again on the basis of stricture type. The class of sonorant consonants can be subdivided into nasals, liquids, and glides (vowels are also sonorants, but not sonorant consonants).