Be cautious; be on guard.

• Use care to avoid danger or trouble.
• Often followed by of, or used alone.

当心；小心；警惕。

• 为避免危险或麻烦而谨慎行事。
• 常与 of 连用，或单独使用。

Be cautious of; guard against (someone or something).

• Used directly without a preposition; formal or literary.

提防某人/某事；对…保持警惕。

• 不接介词直接跟宾语；正式或文学用法。