upon · preposition /əˈpɒn/
once upon a time
B1 used at the beginning of a story to mean a long time ago
Dictionary example:
Once upon a time there was a beautiful princess.
Learner example:
Once upon a time there was a very poor family. (Preliminary English Test; B1; Swiss German)
upon
B2 on
Dictionary examples:
Upon her head she wore a black velvet hat.
Please report to the reception desk upon arrival.
Learner example:
He answered with a smile upon his face, 'As I just told everybody else, you will have the results by the end of June.' (First Certificate in English; B2; Danish)
