> You're right, it's much better, but the entropy of an English word is nowhere near log2(20K) (between 14 and 15 bits of entropy), especially in a grammatically correct sentence, because you're simply unlikely to select them truly randomly.
I've heard the average entropy of English is 3 bits/character, in which case 14-15 bits sounds about right for a word.
I'm not sure your average English word has as much as five characters on average. Okay, let's count this paragraph.
91 characters, in 21 words. 4.3 characters on average, which would mean 13 bits of entropy. I don't believe it. It sounds like your source didn't account for word frequencies in real sentences, let alone grammatical constraints.
I've heard the average entropy of English is 3 bits/character, in which case 14-15 bits sounds about right for a word.