For words that only have 3 letters, there is absolutely no 4th letter. For instance with the word “incorporate”, there won't be any a lot more letters Later on and so should be the word "incorporate". The word “addict” is inside the BIP39 wordlist but you might have used “addi” https://bookmark-rss.com/story18673955/not-known-facts-about-bip39-english-words