[rewboss]

There's no good answer to the question of "how many words are there in the English language?"

Some clever people maintain that the number of words is actually infinite, because you can add suffixes and prefixes to your heart's content, getting a new word every time. However, in practice, once you get past a certain level, the words you form are not useful, and words much longer than that are essentially meaningless. About the longest useful word you could form in this manner is traditionally stated to be "antidisestablishmentarianism", which is opposition to the belief that church and state should be separated; I would tentatively suggest that a group of people who hold such views are "antidisestablishmentarianists", which is one letter longer, but that's about as far as I am prepared to go.

There are a few longer words, but they are mostly technical words specific to certain branches of science (names of organic chemicals can be very long -- but they're not so much words as a sort of scientific code).

Since new words are being coined all the time, and old words falling into disuse, it's hard to put an actual figure on just how many words there are, but "hundreds of thousands" is probably the nearest you'll get to an actual figure.

However, the number of words you'll need to know to be fluent in English is considerably less; mere tens of thousands. About 60,000 if you're a PhD student.