For words that have only 3 letters, there isn't any 4th letter. For example with the word “insert”, there aren't any more letters afterwards and thus have to be the word "incorporate". The word “addict” is inside the BIP39 wordlist however, you might have employed “addi” for “addict”. The way https://franciscougju442.bravesites.com/entries/general/Opening-the-Power-of-BIP39-An-Extensive-Consider-Word-Lists-and-Secure-Budgets