For words that only have 3 letters, there isn't any 4th letter. As an example with the word “include”, there aren't any a lot more letters Later on and therefore should be the word "increase". The word “addict” is during the BIP39 wordlist however, you would've utilised “addi” for “addict”. https://seolistlinks.com/story20304460/how-much-you-need-to-expect-you-ll-pay-for-a-good-valid-bip39-seed-phrase