What's the difference between the subordinate conjunctions when and while?
When & While: The Short Answer
In some sentences, you can use either without a great change in meaning. Generally, if you want to focus on an action that has a duration being in progress, use a while + a progressive tense.
While I was washing the dishes, my wife came home.* (Washing the dishes has a duration, e.g. 4 minutes.)
(*Note you can also use when here, but as a general rule, while is suitable.)
In other cases when you don't need to emphasize that an action was in progress or the action is short and without a significant duration, use when and a simple tense.
When it started to rain, we went inside. (The action started is short; it is not something in progress).
Here are some tips on the use of these two conjunctions.
Tip #1: Use a Progressive (Continuous) Tense with While to Show Focus
Progressive tenses use the BE verb + a verb in ~ing form.
While I was cooking dinner, the phone rang.
I will be sleeping at 11:00 p.m. tonight, so don't phone me.
We use while to focus on an action happening at a specific time. Therefore, the most natural verb tense to use is a progressive tense, which shows that an action is in progress at a certain time.
It is common to use while with actions happening at a specific time (e.g. at 11 p.m.). Also, we use while to show that a shorter action (usually in the past simple, e.g. the phone rang) happened during as a longer action (usually in past progressive, e.g. I was cooking dinner). Often this shorter action interrupts the longer action.
A sensible rule is to use while with the progressive tenses and when with the simple tenses.
Tip #2: Use While with Actions that have a Limited Duration
- When I was a child, I played soccer. (Correct)
While I was a child, I played soccer.(Not natural)
Why is #2 not natural? Well, when an action is too long (e.g. I was a child), we lose focus. The period of twelve years when you were a child is too long to use a progressive tense. We don't use 'while' to talk about long periods of our lives. Instead, we use when and past simple. There's another reason.
Tip #3: Use While with Action Verbs
Also, "While I was a child" is unnatural because the BE verb (was a child) is a state verb. State verbs are not action verbs (e.g. jump, kick, shower, drink). Instead, state verbs describe states or conditions (e.g. BE, live, understand, know, exist). We do not use progressive tenses with state verbs. As a result, we generally don't use while with state verbs.
While she was driving, I played with the radio. (Natural)
This is correct. Driving is an action verb and the action is limited in duration. In other words, driving is a short activity that has a clear start and end.
While When I lived in my hometown, my mother made me dinner. (While is not natural)
Live is a state verb, and also, the action of living in my hometown probably had a duration of 18 years. This is too long to focus on.
Exception: Focusing on a Verb in Progress
You could use while with a state verb like 'live' if you really want to focus on the fact that an action was in progress at a specific time. For example:
While I was living in India, there was a big earthquake.
Although it would probably be more common to use When I lived in India, this sentence is correct. The speaker chooses to use 'While' + present progressive' to focus on an action being in progress (living) when another action happened.
Remember: While Means an Action Had a Start and an End (a Duration)
If a sentence uses while, it suggests that the action happened over a period of time. Here's are two better examples to show what I mean:
When the phone rang, I was making lunch.
The longer action (making lunch) was happening when a shorter action happened (phone rang).
Key question: How many times did the phone ring? Because we're using when, we don't know. The use of when doesn't suggest it was an ongoing action. The phone may have rang once and stopped.
While the phone was ringing, I was making lunch.
How many times did the phone ring here? More than once. Because we are using While + present progressive, we are focusing on duration. This means that the action (ring) happened over a period of time that had a start and end. When we say 'the phone was ringing' in the progressive, we are saying that this happened for some time. (Thanks to Clive at Englishforums for this point.)
While vs. When: In Conclusion
We can conclude the following:
- To emphasize (focus) that an action was in progress at a specific time, use while + a progressive tense ( = While I was eating, ...)
- Otherwise, use when + a simple tense. (= When I ate, ...)
- Verbs with while have a duration. The period of the verb cannot be too long or we lose focus. (=
While I was a child= When I was a child)
- Progressive tenses use action verbs, so use while with an action verb (While I was dancing) and not a state verb (
While I was hungry)
I hope these ideas have been useful. Remember, these are general tips (not fixed rules). There will be exceptions depending on what the speaker wants to emphasize. If you have any questions or comments, please leave them below.
-- Matthew Barton / Creator of Englishcurrent.com