1
be alert to sth
alert to 后接需要警惕的对象。
Drivers should be alert to pedestrians crossing the road.
司机应该对过马路的行人保持警觉。
警觉的；警惕的；注意的
先理解核心含义，再看它在真实句子里的用法。
警觉的；警惕的；注意的
Attentive, awake, and ready to notice danger or opportunities.
Drivers should be alert to pedestrians crossing the road.
司机应该对过马路的行人保持警觉。
警觉的；清醒的；警惕的
Attentive; awake; on guard.
The guard remained alert throughout the night, watching for any unusual activity.
警卫整晚保持警觉，留意任何异常活动。
You need to be alert when driving in heavy rain.
大雨中开车时你需要保持警觉。
A good student is always alert in class, ready to answer questions.
好学生在课堂上总是很留心，随时准备回答问题。
alert to 后接需要警惕的对象。
Drivers should be alert to pedestrians crossing the road.
司机应该对过马路的行人保持警觉。
stay/remain alert 强调保持警觉状态，不接宾语。
Please stay alert while the experiment is running.
实验进行期间请保持警觉。
alert for 后接可能出现的迹象或机会，与 alert to 侧重点略有不同。
Be alert for any signs of leaking gas.
要警惕任何漏气的迹象。
Not this
She always alert in class.
Use this
She is always alert in class.
中文里形容词可直接作谓语，但英语形容词作表语时必须加系动词be，所以应补上is。
Not this
You should be alert of phishing emails.
Use this
You should be alert to phishing emails.
表示“对……警惕”时，alert后接介词to，不接of；of表示所属或来源，不能用来引出警觉的对象。
Focus on the distinctions below. Other candidates are kept compact until a reliable usage note is available.
保持警觉
Please stay alert while driving at night.
夜间开车时请保持警惕。
对…保持警觉
Investors should be alert to market changes.
投资者应对市场变化保持警觉。
警惕…
Be alert for pickpockets in crowded areas.
在拥挤的地方要警惕扒手。
思维敏捷的
Puzzles help keep you mentally alert.
解谜有助于保持思维敏捷。
完全清醒的
The noise made us fully alert.
噪音使我们完全清醒。
警惕着；保持戒备
Be on the alert for pickpockets in the crowded station.
在拥挤的车站要警惕扒手。
处于高度戒备状态
The region remains on high alert after the earthquake.
地震后该地区仍处于高度戒备状态。
红色警报；紧急戒备状态
The city issued a red alert ahead of the typhoon.
台风来临前，该市发布了红色警报。
Use alert naturally, then get feedback on meaning, tone, grammar, and phrasing.
Revisit a common error or keep this word in your review list.
alert 开头 a 像人竖起耳朵，听到风吹草动立刻清醒警觉。
语域：neutral 常见场景：安全提示、日常提醒、正式警告 作形容词时表示“警觉的、警惕的”，语气中性；通常用于 stay/be alert (for/to) 等搭配，在安全提示、日常提醒和正式警告中都比较常见。
常与to连用，表示'对……警觉'；后接that从句。
Dictionary facts from DICTIONARY_API_DEV, ECDICT, WIKTIONARY, WORDNET.