For words that have only 3 letters, there isn't any 4th letter. One example is with the word “incorporate”, there are no additional letters Later on and therefore must be the word "insert". The word “addict” is within the BIP39 wordlist but you might have utilized “addi” for “addict”. You https://socialwebleads.com/story4353561/how-much-you-need-to-expect-you-ll-pay-for-a-good-bip39-definition