determine ambiguous or unambiguous

Question

if any language is given , how we can determine that its grammar is ambiguous or unambiguous

ex.  L = {aⁿbc^m | n > 1, m ≤ n}

its very big confusion for me . please explain in brief ?

Comments

Grammar for the language L, may be ambiguous or unambiguous , depending on Logic of different persons and there may be many grammars for the language. 

In terms of Languages, We have question, that for the given language, there exist any unambiguous grammar, or all (possible) grammars for the language are ambiguous, if all grammars for the language then language will be Inherently Ambiguous.

Now, Concentrate on the Given language, and language is DCFL, so it is conform, there exist an unambiguous grammar for it.

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sir , can we say that , if any variable have two or more possibility , then it is unambiguous

in the following example of even length palindrome

S has 3 choices . then it is ambiguous 

S --> 0S0 | 1S1 | ∈

plz correct me if i m wrong

and what about the following example -

S --> 0S0 | ∈

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Man, you are terribly wrong. 

A Grammar is ambiguous, if there exist at least one string belong to language generated by grammar, having two or more different derivations corresponding to different parse tree. 

Both S $\rightarrow$ 0S0 | 1S1 |$\epsilon$ and S$\rightarrow$0S0 |$\epsilon$ are unambiguous.