(also call upon) To request or ask something of (a person); to select for a task.
To visit (a person); to pay a call to.
(also call upon) To have recourse to.
To correct; to point out an error or untruth.
To select (a student in a classroom, etc.) to provide an answer.
To ask (somebody) to do something.
To ask for (something).
A message sent over a network to a server.
Act of requesting (with the adposition at in the presence of possessives, and on in their absence).
Condition of being sought after.
A formal message requesting something.