bottom

Compared meaning: the buttocks (noun).

比较义项：臀部（名词）。

• seat

  A mild, slightly formal or polite way to refer to the buttocks, often used by doctors, tailors, or in descriptions of clothing fit; rarely used casually among friends.

  指臀部的一种较委婉、略正式的说法，常用于医生、裁缝或描述衣物合身度的场合；朋友间随意聊天时较少使用。

  The doctor asked him to lie on his side and examined the seat area.

  医生让他侧躺，检查了臀部区域。

• bottom 本词

  The everyday, casual word for the buttocks, commonly used with children or in informal conversation; can sound childish or too blunt in formal settings.

  是表示臀部最常见、最随意的口语说法，常用于和小孩说话或非正式场合；在正式场合使用会显得幼稚或过于直白。

  She slipped on the ice and landed right on her bottom.

  她在冰上滑倒，正好摔在屁股上。

Seat and bottom both can mean the buttocks, but seat is a milder, slightly formal word, often used by doctors or tailors. Bottom is the everyday, casual word, common with children or informal talk. This does not compare bottom meaning 'the lowest part'.

两词在“臀部”这个意思上接近，但 bottom 更随意、口语化，seat 略显委婉或正式，常见于医生诊室、裁缝等场合。这里不比较 bottom 的“底部、末端”这一常用义（如例句中包包的底部）。