The expression keep an eye on is a common English idiom that means to watch someone or something carefully, to monitor a situation, or to take care of something temporarily. It implies a level of vigilance or supervision to ensure safety, detect changes, or prevent problems.
This collocation is semi-idiomatic. While the individual words "keep" and "eye" retain some of their literal sense (retaining sight of something), the phrase as a whole functions as a single unit of meaning. In terms of register, it is highly versatile, used frequently in neutral, informal, and professional contexts alike.
The grammatical pattern for this expression is verb + noun phrase + preposition: [keep] + [an eye] + [on] + [object].
These examples are sourced from keep an eye on on Ludwig.guru.
"Keep an eye on him." — nytimes.com
"Keep an eye on your thermostat." — newyorker.com
"Keep an eye on the gold price." — forbes.com
"Keep an eye on traffic." — wikihow.com
"Finally, something to keep an eye on." — forbes.com
Depending on the level of formality or the specific situation, you might want to vary your language.
| Phrase | Context |
|---|---|
| monitor | More formal and technical; often used in scientific, medical, or data-driven contexts. |
| watch over | Implies a sense of protection or guardianship over someone vulnerable. |
| keep track of | Focuses on following the progress, movements, or changes of something over time. |
| look after | Commonly used when taking care of someone's needs, like a child or a pet. |
| keep a lookout for | Emphasizes searching for something specific that is expected to appear. |
| keep tabs on | More informal; often implies monitoring someone's activities closely or suspiciously. |
| Expression | Meaning | Grammatical Pattern | Register |
|---|---|---|---|
| keep an eye on | To monitor or watch someone or something closely | keep + an eye + on + [object] | Neutral / Versatile |
No, the idiom is inseparable and the object must always follow the preposition on. You should never place the object between the words, as in "keep an eye him on," which is grammatically incorrect.
While keep an eye on means to monitor something that is already there, keep an eye out for means to look for something that has not appeared yet. You keep an eye on your luggage at the airport, but you keep an eye out for your friend who is arriving.
Learners often use the plural 'eyes' instead of the fixed singular 'eye' or use the wrong preposition, such as keep an eye for. To sound natural, you must use the singular noun "eye" and the preposition "on" in this specific expression.
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