Books on linguistics and NLP often mention that English is modeled by context free grammars, but also is parsed by LR(k) parsers.

LR(k) parsers are for parsing deterministic CFLs, while CFLs are nondeterministic.

Is English largely a CFL or deterministic CFL?

Or what aspects of English is modeled as a CFL, and what aspect of English is modeled as a deterministic CFL?


1 Answer 1


No natural language is deterministic. What book mentions LR parsers for English?

There might be some “controlled languages” based on English that are deterministic, but a broad-coverage parser is always non-deterministic, there are typically many syntactic ambiguities that get resolved later at the level of semantics or pragmatics.

In actual fact, many parsers use a context-free skeleton with additional constraints for ruling out ill-formed phrases which leads to languages that might be context-sensitive.

  • Thanks. I don't remember well then. So English is modeled as CFL, not deterministic CFL then?
    – Tim
    Jun 14, 2020 at 20:23
  • Yes, it’s CFL, non-deterministic by its very nature.
    – Atamiri
    Jun 14, 2020 at 20:44

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