Cyclopaedia as a noun is an encyclopedia while Encyclopaedia as a noun is a reference work (often in several volumes) containing in-depth articles on various topics (often arranged in alphabetical order or by category) dealing with a wide range of subjects or with some particular specialty
Part of speech: noun
Definition: an encyclopedia
Part of speech: noun
Definition: A reference work (often in several volumes) containing in-depth articles on various topics (often arranged in alphabetical order or by category) dealing with a wide range of subjects or with some particular specialty
We hope you now know whether to use Cyclopaedia or Encyclopaedia in your sentence.