expression

Compared meaning: the emotion shown on someone's face (noun).

比较义项：脸上流露出的神情、表情（名词）。

• look

  Describes the fleeting appearance on someone's face or in their eyes at one moment; casual and physical, typically paired with an adjective, and never used for expressing ideas in words.

  描述某人脸上或眼神中某一刻流露出的短暂神态，语气随意、偏重外在表现，通常与形容词搭配使用，不用于表示用言语表达想法。

  There was a look of confusion in her eyes as she read the strange letter.

  她读那封奇怪的信时，眼中带着一丝困惑的look。

• expression 本词

  Refers broadly to how feelings are shown on the whole face, or even through words and tone; more formal, used in fixed phrases like 'facial expression', and fits when talking about controlling emotion rather than just the eyes.

  泛指整张脸上流露出的情绪，甚至可以指用言语或语气表达情感；语气更正式，常用于「facial expression」这样的固定搭配，也适合表示克制情绪时脸上的样子，而不仅限于眼神。

  He kept a calm expression throughout the entire meeting, hiding his nerves.

  整场会议中，他脸上始终保持着平静的expression，掩饰着内心的紧张。

Look and expression both mean an emotion shown on the face. Look is the fleeting look in someone's eyes, casual. Expression is broader and formal, and can mean expressing ideas in words. Look also means 'style'; expression also means a math term; not compared.

look和expression在表示「神情、表情」时意思相近，都可以形容脸上流露出的情绪；但look更侧重外表或眼神在某一刻呈现的样子，语气较随意，而expression更正式、范围更广，既可以指整张脸的神情，也可以指用言语或语气表达想法。这里不比较expression表示「表达式」（如数学表达式）等其他用法，也不比较look作动词「看」或指「造型、款式」的用法。