As we saw in the previous chapter, plosives and nasals are similar in that they both involve a complete closure between the articulators, preventing air from escaping from the mouth. They are both stops. However, plosives (oral stops) also involve a velic closure between the velum and the back wall of the pharynx, preventing air from escaping through the nose. In short, air does not escape until one of the two closures is released. We can show this in Figure 7.1, which traces the movement of the lips through time for a [ b ] sound, as in abbey [ b i ]. In this, and all subsequent diagrams in this chapter, time goes from left to right. Such diagrams are called parametric, because they plot the state of particular parameters (here, the lips) through time.