1)explaind the meaning of young modulus

Question

2)what do you understand by the modulus of elasticity of a cantilever{practically}
3)what are the precautions observed when performing a cantilever practical
4)what is the conclusion from the practical
please answers are needed immediately

Answer 1

You seem to be using the word "practical" as a noun, although it is an adjective. In plain English, your question does not make sense.
A definition of Youngs modulaus can easily be found with a computer search.

http://en.wikipedia.org/wiki/Young%27s_modulus