The slow neutron capture process, also known as the s-process, is a nuclear reaction in which a neutron is absorbed by a heavy nucleus, causing it to become unstable and emit radiation. This process is responsible for the production of many elements heavier than iron in stars. Some synonyms for the s-process include the slow neutron-capture nucleosynthesis, the s-capture process, and the s-nucleosynthesis. All these terms refer to the same process wherein a slow-moving neutron is captured by a heavy nucleus, and the resulting unstable nucleus undergoes beta decay, leading to the formation of a new element. Although the terminology may differ, the underlying science remains the same.