dear frnd. while is often used, the two action act or happen at the same time. e.g. it ran while I was walking. it means at the same time it ran when I walked (while I was walking.) note it is necessary to use ing form ( going/coming). when is usually used, a action has happened then an other action happened. e.g. you phoned me when I slept. its mean I slept before, then u phoned me. it occasionally takes simple tense (present/past/future or present perfect) not progressive.
↧