For words that have only 3 letters, there isn't any 4th letter. As an example with the word “incorporate”, there are no extra letters Later on and thus must be the word "increase". The word “addict” is from the BIP39 wordlist but you might have used “addi” for “addict”. A https://franciscougju442.bravesites.com/entries/general/Opening-the-Power-of-BIP39-An-Extensive-Consider-Word-Lists-and-Secure-Budgets