- CFG are easy to write and easy to understand and easy to parse with com-pared to more powerful grammars, but they cant always express what is exactly desired
- We cant express English in context free grammar (CFG)
- We cant write CFG for programming languages.
CFG are strictly more powerful than RE.
Any language that can be generated with RE,can be generated by CFG also.
CFG is said to be proper if it has-no unreachable :$\forall,N\in V$: $\exists, \alpha. \beta (VUI)^*:S\Longrightarrow \alpha N \beta$