Let L be an infinite Context Free Language, then there exists some positive integer n
Such that for any string ω ∊ L with |ω| ≥ n, and if we mark at least n positions in ω as distinguished, then we can write ω = uvxyz.
Such that :
Use of Ogden’s Lemma:
Ogden’s lemma can be used to prove the given languages are not Context Free Language, in that case where pumping lemma for CFL fails.
Example:
It is not CFL. This proves is not possible for pumping lemma.