bun

Compared meaning: a small piece of bread (noun).

比较义项：小圆面包（名词）。

• roll

  A general term for any small individual bread portion, often served plain alongside a meal (a dinner roll); can be savory, and its shape is not always perfectly round.

  泛指用餐时搭配的独立小面包，常见于正餐（如 dinner roll），口味多为咸味，形状也不一定是标准的圆形。

  The waiter placed a warm roll beside each dinner plate.

  服务员在每个餐盘旁边放了一个温热的小面包。

• bun 本词

  A soft, round bread piece, often slightly sweet, most typically used to hold a burger or hot dog filling rather than eaten on its own with a meal.

  质地柔软、形状浑圆的小面包，口味常带一点甜味，最典型的用途是夹住汉堡肉饼或热狗，而不是单独作为正餐配食。

  She slid the grilled patty onto a soft bun.

  她把烤好的肉饼放进一个松软的小圆面包里。

Roll and bun both mean a small piece of bread. Roll is a general word for small bread, served with a meal. Bun is a soft, sweet, round bread used for a burger or hot dog. This does not compare roll meaning to turn.

roll 和 bun 都指西式餐桌上常见的独立小面包，但 roll 泛指各种小面包，常见于正餐配餐；bun 则特指质地柔软、略带甜味、最典型用于夹汉堡或热狗的小圆面包。这里不比较 roll 作动词表示“滚动”的义项。