There is no common agreement on the meaning of the word "understand". However, there is agreement on what students should be able to do with material they understand. Bloom et al. discuss kinds of tasks a student should be able to do, provided that the student understands. In a similar way, Biggs and Collis provide a taxonomy intended to evaluate the quality of learning. Both of these taxonomies are intended to fit all subjects. The work here concerns understanding and so is like that of Bloom et al. Some of Bloom's work is reorganized and added to in order to provide different types of questions to test understanding of mathematics.