For words that only have 3 letters, there isn't any 4th letter. For instance with the word “add”, there are no far more letters afterwards and therefore must be the word "incorporate". The word “addict” is in the BIP39 wordlist however you would've utilized “addi” for “addict”. bip39-phrase.com is an https://push2bookmark.com/story19177926/the-ultimate-guide-to-bip39-seed-phrase-github