For words that only have 3 letters, there isn't any 4th letter. For instance with the word “include”, there aren't any more letters afterwards and therefore must be the word "incorporate". The word “addict” is while in the BIP39 wordlist however , you would have made use of “addi” for https://bookmarklinking.com/story5065768/the-fact-about-bip39-seed-phrase-word-list-that-no-one-is-suggesting