For words that only have 3 letters, there is absolutely no 4th letter. For instance with the word “include”, there won't be any additional letters Later on and so has to be the word "add". The word “addict” is within the BIP39 wordlist but you would have utilized “addi” for https://sparxsocial.com/story9097905/an-unbiased-view-of-bip39-seed-phrase-github