For words that have only 3 letters, there's no 4th letter. For instance with the word “include”, there won't be any far more letters afterwards and thus must be the word "incorporate". The word “addict” is while in the BIP39 wordlist however , you would have made use of “addi” https://bookmarkuse.com/story19299823/the-ultimate-guide-to-bip39-seed-phrase-github