A stable isotope refers to a type of atom with a fixed number of protons, neutrons and electrons in its nucleus. Synonymous terms for stable isotopes include non-radioactive isotopes, isotopes with a low decay rate, and isotopes with a high half-life. Stable isotopes are useful in many fields including geology, biology, and chemistry. They are commonly used in radiocarbon dating, nutrient cycling, and tracing metabolic pathways. Additionally, researchers use isotopic analysis to investigate climate change, pollution, and diet. The use of stable isotopes is important in research, as it helps scientists understand the natural processes and effects of human activities on the environment and living organisms.