For words that only have three letters, there's no 4th letter. Such as with the word “increase”, there won't be any far more letters afterwards and so need to be the word "incorporate". The word “addict” is in the BIP39 wordlist however, you might have utilised “addi” for “addict”. - https://pukkabookmarks.com/story19671247/top-guidelines-of-bip39-word-list-pdf