Tony from China writes,
Hi! I am an English learner from China. I want to know the difference between when and while. Thanks!
This is a very interesting question, because both words are what grammar experts call "subordinating conjunctions." That means we use them to connect subordinating clauses to the main clause of a sentence. A subordinating clause is a part of a sentence that adds additional information to the main clause. Here is an example:
I read Tony's email when I started work today.
The main clause is "I read Tony's email." The additional information is "when I started work today." The subordinating conjunction "when" tells us that the time of the second event was almost at the same time or very close to the time of the first event.
Note that both these actions – "start" and "read" are single actions, using verbs in the simple past tense. That is an important thing to remember as we look for the difference between "when" and "while."
Now, look at this example:
While I was making lunch, the phone rang.
Here, the first action is in the present continuous tense. That means the action, making lunch, took place over a period of time. The main clause, "the phone rang" is in the simple past tense, and it is a single action taking place at a point in time.
The order of the events in a sentence with subordinating conjunctions can affect the choice of "when" or "while. If we change the order of our example above, we get:
When the phone rang, I was making lunch.
Here, the conjunction "when" is in the clause with the single action, "the phone rang."
So as a general rule, you should use "while" in a clause with a continuous action, using a verb in a continuous tense. Use "when" in a clause with a single action, using a simple past or present tense.
If you have a question for our staff of teachers, send it by email to www.hxen.com
And that's Ask a Teacher!