For words that only have three letters, there is no 4th letter. Such as with the word “include”, there won't be any additional letters afterwards and therefore must be the word "increase". The word “addict” is during the BIP39 wordlist however, you would've made use of “addi” for “addict”. Artwork https://7bookmarks.com/story18904066/little-known-facts-about-bip39-words