Speakers know that words in their language differ from one another in a restricted number of ways, despite the massive number of degrees of freedom of the human vocal tract.
Language differ in the set of segments that they employ.
Types of gestures Gestures can be characterized in terms of the relative independence of the articulators that are used to control their constrictions. Gestures involving constrictions of these three structures involve completely distinct, non-overlapping sets of articulators. Such alternations are typically not restricted to individual lexical items, but are general patterns exhibited by all lexical items that share some critical phonological property. The target becomes more like the trigger. They occur more in fluent, casual speech styles.