"Pharmacology: An Introduction" is a part of the college-level Neuropsychopharmacology course series textbooks. It is a tutorial written in questions and answers format to introduce the basic principles and concepts in pharmacology, drug interactions and drug-binding. It is a study guide with in-depth explanations. Each section is a modular unit that is self-contained for easy reading. The principles and concepts are introduced systematically so students can learn and retain the materials intuitively.