For words that only have three letters, there is no 4th letter. One example is with the word “include”, there aren't any much more letters Later on and thus must be the word "add". The word “addict” is during the BIP39 wordlist however you would have made use of “addi” http://zanevnex175.lowescouponn.com/unlocking-the-power-of-bip39-an-extensive-consider-word-lists-and-secure-pocketbooks