Zi Collection, Page Position: Upper, Radical: Mouth (kǒu), Page 10, Entry 01 Pronounced ku (falling tone) Meaning: To labor diligently. "The Book of Definitions" (Boya) explains it as to diligently exert one's strength. "The Jade Seal" (Yupian) explains it as to exert strength. Zi Collection, Page Position: Upper, Radical: Mouth (kǒu), Page 10, Entry 02 Pronounced kuo (falling tone) Meaning: The same.