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*List down the features of Probabilistic Context Free Grammars (PCFGs)*

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__Question:__

### What are the features of Probabilistic Context Free Grammars?

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__Answer:__

- Partial solution for grammar ambiguity. A PCFG gives some idea of different reasonable parses.

- PCFG is not lexicalized since its probability estimates are based purely on structural factors.

- Robustness – the problem of grammatical mistakes, and errors in the real texts can be avoided by assigning low probability for non-reasonable (not probable) sentences. That is, PCFG admits everything with low probability.

- Gives a probabilistic language model for English.

- Predictive power of PCFG is comparatively better than that of HMM.

- An n-gram language model considers some local lexical context while measuring the probability of a sentence, whereas a PCFG does not consider the lexical information. Hence, PCFG is worse model than any n-gram model for English.

- In PCFG, the probability of smaller trees are greater than the larger trees.

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