Relative clauses are useful for differentiating clearly between similar ideas. Exercises that demonstrate this purpose of relative clauses, or other grammatical constructions, can provide useful practice for students. More generally, an approach to teaching grammar that asks what purpose a structure serves can enable teachers to design exercises that demonstrate function as well as form. Exercises for relative clauses might include the presentation of situations in which the student must choose between two options and respond by using a relative clause with "that,""whose,""where," or "who," or by repeating a single form in different situations. The significant difference between these exercises and pattern drills is in the de-emphasis of form and the emphasis on the function of the structure. Exercises for other structures can be developed similarly, with the questions of what the structure is good for, and under what circumstances it is needed as the starting point. (MSE)