Science, Tech, Math › Science Residue Definition (Chemistry) What Is a Residue? Share Flipboard Email Print A residue can be an undesirable by-product of a chemical reaction. C. Allan Morgan / Getty Images Science Chemistry Chemical Laws Basics Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated July 03, 2019 Residue Definition: Residue has several meanings in chemistry. Residue is the matter left in a container after evaporation or distillation has occurred.Residue is the undesirable byproduct of a chemical reaction.Residue is recognizable molecular part of a larger molecule. For example, an amino acid is the residue of a larger protein chain.