For words that have only 3 letters, there is not any 4th letter. One example is with the word “include”, there isn't any far more letters Later on and thus must be the word "increase". The word “addict” is while in the BIP39 wordlist but you might have used “addi” https://letsbookmarkit.com/story18767342/little-known-facts-about-bip39-words