informal

Compared meaning: relaxed and not formal (adjective).

比较义项：轻松、不正式的（形容词）。

• casual

  Describes a relaxed, easygoing manner or attitude, often about clothing, behavior, or one's approach to a situation; suggests not caring much or not taking something seriously.

  形容一种轻松随意的举止或态度，常用于穿着、行为或对待某事的方式；暗示不太在意或不太认真对待。

  He has a casual attitude toward deadlines that annoys his stricter coworkers.

  他对截止日期的态度很随意，这让他那些更严格的同事很恼火。

• informal 本词

  Describes the absence of formal rules, structure, or ceremony in an occasion, setting, or way of speaking; focuses on the setting or register rather than personal attitude.

  形容某个场合、环境或说话方式缺乏正式的规则、结构或礼节；侧重场合或语体，而非个人态度。

  Try not to use overly informal language in a professional email.

  在正式邮件中不要使用过于非正式的语言。

Casual and informal both mean relaxed and not formal. Casual describes a person's relaxed attitude, clothing, or behavior, often not serious. Informal describes a setting or way of speaking lacking formal rules, about the situation, not the person. Casual can mean 'occasional work'; not compared.

这两个词在“轻松、非正式”这一义项上很接近，但casual更强调人的态度、穿着或行为方式放松随意、不严肃认真；informal更强调场合、语言或规则缺乏正式性和礼节，侧重的是场合本身而非个人态度。这里不比较casual的其他义项，如“偶然的，临时性的”（如casual worker临时工）。