USE WHEN OR WHILE
When and while function as subordinating conjunctions and is used to introduce an adverbial time clause. It indicates during the time that and shows the action is or was happening when the other action occurred:
- The phone rang when / while she was doing the laundry.
- When / While she was doing the laundry, the phone rang.
Similarly, as and whilst are used in the same way. As and whilst’s tone is rather more formal or literary.
- As the car drove away, I watched him leave.
- I watched him leave whilst the car drove away.
During is a preposition that introduces a longer duration. It is used with either a noun or a noun phrase:
- I learned how to cook paella during my stay to Spain.
- I learned how to cook paella while I was staying in Spain.
ONLY USE WHEN
When is used and not while, when trying to express that the action happens simultaneously as the longer one or the event that is referred to in the main clause:
- He was surprised when Martin told him he got promoted.
- He was still sleeping deeply when his alarm went off.
Moreover, when and not while is used to express that one action happens subsequently after another and to talk about duration in the past.
- When it started raining, everyone hurried home.
- When she was a little girl, rainy days were very often but that was just for several weeks.
Instead of using when, we can use whenever to mean every time that:
- I always turn off the light when I leave the room.
- I always turn off the light whenever I leave the room.
ONLY USE WHILE
We often use while when talking about the longer action of two events or when talking about two longer actions that occur at the same time:
- Martin called while Kara was at work.
- While they were planning the next project, the other team was brainstorming.
- Linda cleaned the room while Margaret watered the flowers.
Keep in mind that even though we usually use a progressive tense, it is also possible to use simple tenses to talk about longer action involving a while time clause.
Furthermore, if the main and subordinate clauses have the same subject, you may leave out the subject and verb be in the when- and while-clause:
- When (you are) studying, be very focused.
- He bumped into an old friend while (he was) sightseeing in Milan.
USE WHILE TO SHOW CONTRASTING IDEAS
We do not only use while to introduce an adverbial time clause. It is often used more formally to connect or balance contrasting ideas:
- While they are upset about the bad news, they don’t want to show it.
- While they have been happily married so far, there will definitely be moments when they must prepare for tough times.
In the examples above, the while-clause is usually placed first of the two contrasting ideas.
MEANWHILE MEANS “DURING THIS TIME”
Meanwhile or during this time, is a linking adverb which is used to link and contrast ideas between two sentences. It is used to express that two events are happening simultaneously:
- Prepare the marinade. Meanwhile, mise en place all the other ingredients.
- Do your homework. Meanwhile, I’ll prepare some snacks.
A WHILE = A SHORT TIME
In cases when while are used as a noun, almost always, it is used with an indefinite article:
- I haven’t read a book for a while. What have I been doing?
- Let’s just stay here a little while longer. It’s so relaxing here.