* Constantly Evolving: New words are constantly being created, while others fall out of use. Dictionaries are constantly being updated.
* Different Sources: Different dictionaries have varying word counts due to their inclusion criteria (technical terms, slang, etc.)
* Defining "Word": What constitutes a word can be subjective. Do we count proper nouns, technical terms, or hyphenated words?
Estimates:
* The Merriam-Webster Dictionary claims to have over 470,000 entries.
* The Oxford English Dictionary has over 600,000 entries, but includes historical and archaic terms.
Conclusion: While there are estimates, a precise number of words in English is impossible to determine. The language is dynamic and constantly changing.