This article series aims to eliminate usage errors and help non-native speakers to write clearly and fluently. We suggest that you always do proper research and use style guides effectively. For anything you are not sure of, feel free to ask us.
“As” is sometimes used to mean “because.” But do not use it if there is any chance of ambiguity. In the example below, “as” could mean “because” or “when.”
Avoid “We canceled the picnic
as it began raining.”
Use “We canceled the picnic because it began raining.”
A Writer’s Reference by Diana Hacker [Sixth Edition]