Tolerance refers to the ability:
to tolerate large doses of drugs without impairment of psychological or physical abilities.
a strong psychological desire and craving for a drug.
the property of a drug that requires increasingly higher levels to get the same effect.
the property of a drug that requires changes in the body's physical functioning, making the drug necessary for normal functioning.

to tolerate large doses of drugs without impairment of psychological or physical abilities.

Explanation:

In simple words, tolerance refers to the capacity of an individuals body to tolerate the urge to consume a specific drug under certain circumstances or the ability of its body to handle the impact of that drug on it.

That's why Strong drugs that are used for curing purposes of serious medical conditions should not be used in overly manner and prescription and guidance from doctor should be made first as this requires very high tolerance which is not present in human body.                  

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