For words that have only 3 letters, there is absolutely no 4th letter. As an example with the word “add”, there are no extra letters afterwards and so have to be the word "incorporate". The word “addict” is from the BIP39 wordlist but you would've utilized “addi” for “addict”. How https://hyperbookmarks.com/story18945225/the-ultimate-guide-to-bip39-seed-phrase-mnemonics-generator