It is hard to deny that we use a lot of linking words in English tests, such as “because of” and “as well as”. Besides knowing their synonyms, a lot of students do not know how to use them in sentences. We are going to introduce you the difference among “when”, “while” and “as”.


1. “When/as” implies a causal relationship between two things: when X happens, Y happens.


It was raining hard as we arrived.


When I got home, he called me.


2. “While” is used only about a continuous state, and another event or state that happens during that time.


I kept silent while he was writing.


My roommate was singing loudly in the living room while I was studying in my room.


3. When “as” is used about time, it implies two events or states happening by chance at the same time.


Things are getting better and better as time goes on.


4. “When” is used when two actions take place in sequence.


I will go home when he comes back.


5. “When” and “while” can be used as parallel conjunctions.

“When” means at this moment/suddenly; “While” means and/but.


We were about to start when it began to rain.


He likes coffee, while she likes tea.