For words that have only three letters, there is not any 4th letter. Such as with the word “increase”, there aren't any extra letters afterwards and thus should be the word "incorporate". The word “addict” is inside the BIP39 wordlist however you might have utilized “addi” for “addict”. By following https://thebookpage.com/story4379086/considerations-to-know-about-bip39-word-list-pdf