I have read a number of scientific papers, and I could go with 5,000 but not half a million. Even if they meant "words and phrases".
Well, I ain't sayin she's all that, but according to Google Assistant, using the second edition of the Oxford dictionary, the english language contains 171,476 words in current use, and 47,156 obsolete words...
That doesn't include redneck variations (which Google Assistant can't even understand) though...