Quick answer: “Keep an eye on” means to watch or monitor someone or something carefully and attentively, often over a period of time.
Keep an eye on means to watch or monitor someone or something with care and attention, often to ensure safety, prevent problems, or track developments. It implies ongoing, attentive observation rather than a single glance.
Meaning
"Keep an eye on" expresses the idea of sustained, purposeful observation. When you keep an eye on something, you are not just looking at it once — you are maintaining a degree of vigilance over time. The phrase is used for protective watching (keep an eye on the children), supervisory monitoring (keep an eye on the budget), or attentive tracking (keep an eye on the news).
The idiom can be used in requests, commands, or statements. It is one of the more transparent idioms in English — even learners who have never encountered it can often guess the meaning from context — but knowing the correct fixed form ("keep an eye on", not "keep eyes on" or "keep a look on") is essential for accurate use.
Origin & History
The idiom draws on the natural metaphor of directing your eye — your attention and focus — towards something and keeping it there. The use of "eye" as a metaphor for attention and awareness is ancient, appearing in expressions across many languages. In English, the concept of "keeping" your eye on something (maintaining that directed attention rather than letting it wander) has been in use since at least the 17th century.
Related expressions include "set eyes on" (to see for the first time), "have an eye for" (to be skilled at noticing), and "catch someone's eye" (to attract attention). "Keep an eye on" is the most practical and widely used of this cluster, appearing in everyday conversation, workplace communication, and literary English alike. Reference works such as the Cambridge Dictionary catalogue thousands of such figurative expressions, showing how idiomatic meanings take shape over time.
Example Sentences
| Sentence | Context |
|---|---|
| Could you keep an eye on my bag while I go to the counter? | Everyday request, personal safety |
| The manager asked her to keep an eye on the new recruit's progress. | Workplace, supervision |
| We need to keep an eye on competitor pricing over the next quarter. | Business, market analysis |
| Keep an eye on the weather forecast — we may need to cancel the outdoor event. | Event planning, contingency |
Dialogue Example
A: "I'll be back in ten minutes. Can you keep an eye on the kids?"
B: "Of course. Don't worry, I'll make sure they don't get into trouble."
A: "They're in the garden. Just make sure they don't go near the gate."
B: "I've got them. Take your time."
Usage Notes
"Keep an eye on" works in both formal and informal English. In formal writing, you might prefer "monitor", "supervise", "track", or "maintain oversight of". In spoken and semi-formal contexts, "keep an eye on" is natural and widely understood.
The object follows directly after "on": "keep an eye on [something/someone]". The phrase can be used in imperative form ("Keep an eye on..."), as a request ("Could you keep an eye on...?"), or as a statement ("I'm keeping an eye on..."). All three tenses work naturally with this idiom.
Common Mistakes
Mistakes to Avoid
Please keep eyes on the presentation while I step out.
Please keep an eye on the presentation while I step out. — The fixed form is "an eye" (singular with the article "an"), not "eyes" (plural). Changing this makes the idiom unrecognisable.
She kept a look on the situation carefully.
She kept an eye on the situation carefully. — "Keep a look on" is not an idiom in English. The correct phrase is "keep an eye on".
Keep an eye at the clock so we don't run late.
Keep an eye on the clock so we don't run late. — The correct preposition is "on", not "at". The full structure is "keep an eye on [object]".
Practice
Similar Idioms
Practice English Idioms
Use these exercises to master idioms in context:
Want to understand the grammar behind this? Explore our Grammar guides.
Quick Check: Keep an eye on
2 questions — test what you just learned.
1. What does “Keep an eye on” mean?
2. Complete the sentence: “Could you _____ my bag while I go to the counter?”
Frequently Asked Questions
What does "keep an eye on" mean?
"Keep an eye on" means to watch or monitor someone or something with care and attention, often over a period of time. It implies sustained, purposeful observation — you are maintaining vigilance rather than merely glancing at something once.
Where does "keep an eye on" come from?
The phrase uses "eye" as a metaphor for directed attention — a concept found across many languages and cultures. In English, "keeping" your eye on something means maintaining that directed focus rather than letting it wander. The idiom has been in use since at least the 17th century and is one of a large family of English eye-metaphor expressions.
Can you give an example of "keep an eye on" in a sentence?
"Could you keep an eye on my bag while I go to the counter?" Another example: "We need to keep an eye on competitor pricing over the next quarter."
Is "keep an eye on" formal or informal?
It works in both registers. In formal professional contexts it is widely accepted — you will see it in business emails and reports. In very formal or academic writing, "monitor", "supervise", or "maintain oversight of" may be preferred. In everyday spoken English, "keep an eye on" is perfectly natural.
What CEFR level is "keep an eye on"?
B2, though many B1 learners also encounter and understand it. The idiom is relatively transparent — most learners can guess the meaning from context. However, mastering the fixed form (singular "an eye", preposition "on") and using it correctly in all tenses requires upper-intermediate proficiency.
Can I say "keep eyes on" instead of "keep an eye on"?
No. The idiom always uses the singular form "an eye" with the indefinite article. "Keep eyes on" is not idiomatic and will sound unnatural to a native speaker. The fixed form "keep an eye on" must be learned as a whole phrase.
What preposition follows "keep an eye"?
Always "on". The complete phrase is "keep an eye on [object]". Common errors include using "at" ("keep an eye at") or "for" ("keep an eye for"), both of which are incorrect in this idiom. The preposition "on" is fixed.
What are common mistakes with "keep an eye on"?
Common errors include: pluralising "eye" to "eyes", using the wrong preposition ("at" or "for" instead of "on"), and confusing it with "keep a lookout for" (watching for something that might appear) — which has a slightly different meaning. Always use the exact form "keep an eye on".
What are similar idioms to "keep an eye on"?
Similar expressions include "keep tabs on" (to monitor closely), "watch over" (to look after protectively), "keep a close watch on", and "monitor". "Keep an eye out for" is a related phrase meaning to watch for the arrival or appearance of something specific.
How do I practise using "keep an eye on"?
Write three sentences: a request ("Could you keep an eye on...?"), a statement ("I'm keeping an eye on..."), and a past description ("She kept an eye on..."). Use different objects in each sentence — a bag, a project, a situation. Then try LexFizz Flip Tiles to practise the idiom in context.