english (200 questions)
Puzzles that crucially depend on some feature of the English language or that only work in an English formulation.
language (131 questions)
A puzzle that heavily depends on linguistic features; for instance it may concern foreign languages, or only work in some particular language, or be built around a peculiarity of the English language.
Having read the tag wiki excerpts and looked at how these tags are being used ... I don't get it. It seems as though english should be a strict subset of language, but there are many english questions not tagged language, and many English-specific language questions not tagged english.