Several high-quality, openly licensed (or low-cost) lists exist:
Many schools teach "sight words" (Dolch or Fry lists), which usually cap out at 1,000 words. The flaw with those lists is that they leave you functionally illiterate. 5000 most common english words list
Consider this sentence: "The hypothesis was rejected due to insufficient empirical evidence." ⚠️ Avoid: Outdated lists from 1990s textbooks, words
If you only know 1,000 words, you might know the, was, due, to, and evidence, but you will miss the entire scientific meaning (hypothesis, rejected, insufficient, empirical). The 5000 most common English words list includes all four of those critical words. or lists without parts of speech.
⚠️ Avoid: Outdated lists from 1990s textbooks, words like “thy” or “thus” ranked too high, or lists without parts of speech.