This ninth edition of Calculus maintains those aspects of previous editions that have led to the series' success-we continue to strive for student comprehension without sacrificing mathematical accuracy, and the exercise sets are carefully constructed to avoid unhappy surprises that can derail a calculus class. However, this edition also has many new features that we hope will attract new users and also motivate past users to take a fresh look at our work. We had two main goals for this edition: � To make those adjustments to the order and content that would align the text more precisely with the most widely followed calculus outlines. � To add new elements to the text that would provide a wider range of teaching and learning tools. All of the changes were carefully reviewed by an advisory committee of outstanding teachers comprised of both users and nonusers of the previous edition. The charge of this committee was to ensure that all changes did not alter those aspects of the text that attracted users of the eighth edition and at the same time provide freshness to the new edition that would attract new users. Some of the more substantive changes are described below.