他坐在椅子上，屁股很痛。
tā zuòzài yǐzǐ shàng ， pìgǔ hěn tòng 。
He is sitting on the chair, and his buttocks hurt a lot.
小狗喜欢在草地上打滚，屁股上沾满了泥土。
xiǎogǒu xǐhuān zài cǎodì shàng dǎgǔn ， pìgǔ shàng zhān mǎnle nítǔ 。
The puppy likes to roll on the grass, and its bottom is covered with dirt.
他穿得太紧，屁股非常不舒服。
tā chuāndé tàijǐn ， pìgǔ fēicháng bù shūfú 。
He is wearing too tight clothes, and his buttocks feel really uncomfortable.