For words that have only 3 letters, there's no 4th letter. As an example with the word “include”, there isn't any much more letters Later on and thus must be the word "incorporate". The word “addict” is inside the BIP39 wordlist but you might have utilized “addi” for “addict”. Standard https://tbookmark.com/story18694205/considerations-to-know-about-bip39-word-list-pdf