For words that have only 3 letters, there is not any 4th letter. As an example with the word “incorporate”, there won't be any much more letters Later on and therefore need to be the word "incorporate". The word “addict” is within the BIP39 wordlist however , you would've employed https://highkeysocial.com/story4281699/considerations-to-know-about-bip39-word-list-pdf