spectrum: p τ, and the radical words are simplified as τ. Save strokes and simplify according to ancient calligraphy. Original meaning: a systematic list according to the category of things. Such as: chronology, genealogy, cookbooks, cookbooks, genealogy.
extension: extension refers to symbols or graphics that record music, chess games, etc. Such as: music score, music score, chess score, painting score, clef, and music table.