For words that have only 3 letters, there is absolutely no 4th letter. For instance with the word “incorporate”, there won't be any a lot more letters afterwards and so must be the word "increase". The word “addict” is inside the BIP39 wordlist but you would have applied “addi” for https://bookmarklinking.com/story4975577/5-simple-techniques-for-bip39-seed-phrase