In this case, it is obvious that the child is not attempting to state this proposition simply and clearly, and the same goes for the teacher. Since the children have learned all of the terms "vertex,” “base," “perpendicular,” and "straight line," they should be taught to say: "A straight line drawn from the vertex perpendicular to the base is the axis of symmetry." For this reason, instead of picking up on the real intent behind a child's ambiguous statements and explaining things on the blackboard as described above, the teacher should help the child understand how ambiguous his or her statements are by asking questions about the ambiguous points. Children can be taught to think of more accurate and concise statements in this way. This is a method of cultivating the right type of attitude, by which they understand and rediscover the importance and convenience of terms, and understand the benefits of thinking that symbolizes.