A single Chinese word (character) that represents Guanyin’s scripture or essence of prayer, the most fitting one is:
「悲」 (bēi) It means compassion or merciful sorrow — the heart of Guanyin’s vow to relieve suffering. However, if you mean the name of Guanyin’s main scripture, that would be: 《普門品》 (Pǔ Mén Pǐn) It’s the “Universal Gate Chapter” from the Lotus Sutra (法華經), the most famous scripture devoted to Guanyin. the most sacred and …