For words that have only 3 letters, there is no 4th letter. Such as with the word “add”, there isn't any far more letters Later on and therefore needs to be the word "incorporate". The word “addict” is inside the BIP39 wordlist however , you would've utilized “addi” for “addict”. https://bookmarkyourpage.com/story4349870/the-fact-about-bip39-seed-phrase-word-list-that-no-one-is-suggesting