They were upset because of the delay.
They were upset because they were delayed.
Preposition: because of
Conjunction: because
Meaning: for this reason
Despite the rain, we enjoyed ourselves.
Although it rained, we enjoyed ourselves.
Preposition: despite
Conjunction: althopugh
Meaning: in spite of this
We stayed indoors during the storm.
We stayed indoors while the storm raged.
Preposition: during
Conjunction: while
Meaning: at the time when.
It looks like rain.
It looks as if it will rain.
Preposition: like.
Conjunction: as if.
Meaning: in a similar way.