Examples of using "предупреждать" in a sentence and their english translations:
I won't warn you again.
I don't want to have to warn you again.
Are you going to warn them?
Are you going to warn him?
Are you going to warn her?
The Greeks invented the comma, not for their literature but for their actors, to warn them to take a deep breath in preparation of an upcoming long phrase; thus a comma represents a pause.