• an action that was interrupted by another action.
one of his students came in with a
surprise.
• parallel actions happening in the past.
• an action that was in progress at a specific time.
near the exit at Shibuya train station.
NOTE:
We use only
when to present a shorter action.
When he arrived at the station, the dog was waiting
for him.
***
We use both
when and
while to present a longer action.
While the dog was waiting at the station, people were
looking at it.
When the dog was waiting at the station, people were
looking at it.
We can use
when and
while at the beginning or in the middle of the sentence.
Put a comma if you use
when and
while at the beginning of the sentence.
Don't put a comma if you use
when and
while in the middle of the sentence.
When he arrived at the station, the dog was waiting
for him.
The dog was waiting for him
when he arrived at the
station.