Warnings and Messages

The Wolfram Language usually goes about its work silently, giving output only when it has finished doing the calculations you asked for.

However, if it looks as if the Wolfram Language is doing something you definitely did not intend, Wolfram Language will usually print a message to warn you.

The square root function should have only one argument. The Wolfram Language prints a message to warn you that you have given two arguments here.
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You can suppress the message for one evaluation using Quiet.
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The message reappears without the use of Quiet.
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Each message has a name. You can switch off messages for all evaluations using Off.
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The message Sqrt::argx has now been switched off, and will no longer appear.
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This switches Sqrt::argx back on again.
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Quiet[expr]evaluate expr without printing any messages
Off[Function::tag]switch off (suppress) a message
On[Function::tag]switch on a message

Functions for controlling message output.