For words that only have 3 letters, there is no 4th letter. As an example with the word “incorporate”, there are no extra letters afterwards and so has to be the word "add". The word “addict” is from the BIP39 wordlist but you would've utilized “addi” for “addict”. By next https://franciscougju442.bravesites.com/entries/general/Opening-the-Power-of-BIP39-An-Extensive-Consider-Word-Lists-and-Secure-Budgets