屁股

摔疼了屁股

shuāi téng le pìgu

I sat down and my butt ached

坐一会儿屁股都麻了

zuò yíhuìr pìgu dōu má le

I sat for so long that my butt went numb

屁股后面跟着

pìgu hòumiàn gēnzhe

follows behind the buttocks