Cancer radiotherapy is an important component of cancer treatment that uses high-energy radiation to kill cancer cells. There are several synonyms for cancer radiotherapy that can be used interchangeably, including radiation therapy, radiotherapy, and radiation oncology. Some other related terms include external beam radiation therapy, brachytherapy, and proton therapy. External beam radiation therapy involves directing radiation from a machine outside the body, while brachytherapy and proton therapy involve implanting radiation sources or using proton beams to target cancer cells. The goal of all of these treatments is to destroy cancer cells and shrink tumors in a way that minimizes damage to healthy tissue.