For words that have only three letters, there is absolutely no 4th letter. Such as with the word “include”, there isn't any a lot more letters Later on and therefore has to be the word "include". The word “addict” is in the BIP39 wordlist however , you might have made https://moodjhomedia.com/story2657389/little-known-facts-about-bip39-seed-phrase-list