For words that have only three letters, there is no 4th letter. As an example with the word “add”, there isn't any additional letters Later on and therefore must be the word "include". The word “addict” is inside the BIP39 wordlist however you might have utilized “addi” for “addict”. To https://socialmphl.com/story20996135/the-ultimate-guide-to-bip39-seed-phrase-mnemonics-generator