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call on

part of speech: phrase
definition 1: to put out an official demand to (a person, agency, institution, or the like).
The protesters called on the government to put an end to the war.
definition 2: (of a teacher or the like) to ask for a response from or give permission to speak.
He didn't know the answer, and he hoped the teacher wouldn't call on him.She had her hand up a long time, but the teacher never called on her.
definition 3: to summon or ask for help from.
I'm usually the one she calls on when there is some kind of emergency.You're lucky that you can call on your neighbor if anything happens.I want you to know that you can always call on me if you need anything.
definition 4: (chiefly British) to make a short visit to.
We decided to call on a couple of old friends when we were in Chicago.