Read this: Chinese character dictionaries often allow users to locate entries in several ways. Many Chinese, Japanese, and Korean dictionaries of Chinese characters list characters in radical order: characters are grouped together by radical, and radicals containing fewer strokes come before radicals containing more strokes (radical-and-stroke sorting). Under each radical, characters are listed by their total number of strokes. It is often also possible to search for characters by sound, using pinyin (in Chinese dictionaries), zhuyin (in Taiwanese dictionaries), kana (in Japanese dictionaries) or hangul (in Korean dictionaries). Most dictionaries also allow searches by total number of strokes, and individual dictionaries often allow other search methods as well.
Now answer this question, if there is an answer (If it cannot be answered, return "unanswerable"): What is grouped together by radicals?
characters