For words that have only three letters, there is no 4th letter. For example with the word “increase”, there aren't any a lot more letters Later on and thus needs to be the word "include". The word “addict” is within the BIP39 wordlist however, you would have employed “addi” for https://onelifesocial.com/story4148483/facts-about-bip39-seed-phrase-github-revealed