Science, Tech, Math › Science Definition of Moiety Share Flipboard Email Print 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. 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. Updated March 08, 2017 Definition: Moiety is a specific group of atoms within a molecule that is responsible for characteristic chemical reactions of that molecule. Also Known As: functional group Examples: hydroxyl moiety: -OHaldehyde moiety: -COH Continue Reading