For words that have only 3 letters, there's no 4th letter. Such as with the word “include”, there are no extra letters afterwards and thus must be the word "increase". The word “addict” is while in the BIP39 wordlist however , you might have applied “addi” for “addict”. Using BIP44 https://socialfactories.com/story4617378/considerations-to-know-about-bip39-word-list-pdf