Classical poetry theory. 脚韻 ('end rhyme') contrasts with 頭韻 ('alliteration, head rhyme'). 平仄 (ひょうそく) refers to the tonal patterns required in regulated Chinese verse — 'level and oblique' tones, a complex system essential to 絶句 and 律詩. 漢詩 ('Chinese poetry') in Japanese specifically refers to classical Chinese verse as studied in Japan.