Ask a linguist "How many words are there in English?" and watch their face. You'll get a pained expression, then a long pause, then something like "Well... it depends what you mean by a word." This is not evasiveness. It's a genuine philosophical problem that has bedeviled lexicographers for centuries. The number of English words is not a fact waiting to be discovered โ it's a judgment call, and reasonable people disagree by hundreds of thousands.
The Dictionary Problem
Let's start with the simplest possible approach: count all the words in the biggest dictionary. The Oxford English Dictionary (OED) โ widely considered the most comprehensive historical dictionary of English โ contains about 600,000 entries. Merriam-Webster's unabridged dictionary has about 470,000. These numbers seem precise, but they're not. Every dictionary makes editorial decisions about what counts as a separate entry. Does "run" (to move quickly) and "run" (to operate a machine) count as one word with multiple meanings, or two different words that happen to be spelled the same? The OED lists 645 distinct meanings for "run" โ a number so large it seems like a joke, but it's not. Is that one word or 645?
Then there are inflected forms. "Run," "runs," "running," "ran" โ four different word-forms of one "lexeme" (the abstract word). Most dictionaries count these as one word under the headword "run." But languages like Finnish and Turkish have thousands of possible inflected forms per verb. If you counted every single inflected form as a separate word, the numbers would explode. English is relatively tame in its inflection compared to many languages, so lexicographers get away with counting headwords. But even then, where do you draw the line? Is "happiness" a separate word from "happy," or just a suffix added to an existing word?
The Obsolete Word Problem
Words don't die; they just stop being used. But when? No official governing body declares a word officially dead. The word "forsooth" (meaning "in truth") was common in Shakespeare's time. Almost nobody uses it today except ironically. Is it still an English word? What about "thou" and "thee"? They survive in religious contexts, Shakespeare productions, and a few regional dialects. Are they "in" the language or "out" of it? Dictionary editors agonize over these decisions, and different dictionaries make different calls, which is why their word counts differ.
The OED, being a historical dictionary, takes a generous approach โ it includes words that were used at any point since about 1150 AD, even if they've been obsolete for centuries. A standard college dictionary, on the other hand, focuses on words a reader might actually encounter today. This is one reason the OED claims 600,000 while Merriam-Webster claims 470,000. Neither number is wrong; they're answering different questions.
The New Word Problem
English adds words constantly. The Global Language Monitor, a somewhat controversial organization that tracks English usage, estimates that a new English word is created every 98 minutes โ about 5,400 per year. Most of these are technical terms, slang, or brand names that never make it into dictionaries. But some do. "Selfie" was added to the OED in 2013. "Unfriend" (verb) was added by multiple dictionaries in 2009. "Hangry" (angry because hungry) was added in 2018. "Covid" and its derivatives essentially created an entire new sub-vocabulary in a matter of months in 2020.
And then there are the creations that exist in a gray area: "yeet" (a versatile exclamation/verb of enthusiasm or forceful throwing), "no cap" (meaning "no lie" or "for real"), "rizz" (charisma or charm โ short for charisma, and named Oxford's 2023 Word of the Year). These are words that millions of people use regularly but that some dictionaries still haven't formally admitted. Are they English words? If your criteria is "do people use them and understand them?", then yes. If your criteria is "are they listed in a major dictionary?", then... it depends which dictionary and when you check.
The Scientific Name Problem
Here's where counting completely breaks down: scientific and technical vocabulary. The International Union of Pure and Applied Chemistry (IUPAC) has a systematic naming convention for chemical compounds. Using this system, you can generate a chemically valid name for any possible molecule โ and there is no theoretical limit on how long that name can be. The protein commonly called "titin" has a full chemical name that is 189,819 letters long. Is that one word? If it is, and if we count all the possible chemical compound names that could be generated by the IUPAC system, the number of possible English "words" is โ literally โ infinite. Most lexicographers sensibly exclude systematic scientific nomenclature from word counts, but the fact that you have to explicitly exclude it demonstrates how slippery the question is.
What Counts As English, Anyway?
English has borrowed so heavily from other languages that the boundary between "English word" and "foreign word used in English" is fuzzy. "Schadenfreude" is a German word, but it's used in English without translation. "Sushi" is Japanese. "Ballet" is French. "Piano" is Italian. At what point does a borrowed word become an English word? When it's common enough that an average English speaker understands it without explanation? When it appears in an English dictionary? When it's used in an English sentence without italics or translation? There's no consensus.
My personal answer โ and I should be clear that this is an opinion, not a settled fact โ is that English probably has somewhere between 500,000 and 750,000 "words" in any reasonable sense, with perhaps 170,000 in active current use by an average educated speaker. The precise number doesn't actually matter. What matters is that English has, by any measure, one of the largest vocabularies of any language in history โ and that's a direct result of its willingness to absorb, create, and endlessly repurpose words from every language it encounters.