For words that only have three letters, there is no 4th letter. One example is with the word “include”, there isn't any additional letters afterwards and so must be the word "increase". The word “addict” is from the BIP39 wordlist however, you might have utilized “addi” for “addict”. Many Wallets:In https://bookmarkfly.com/story19049696/the-ultimate-guide-to-bip39-seed-phrase-github