For words that only have 3 letters, there is no 4th letter. Such as 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 made use of “addi” for “addict”. https://wearethelist.com/story20670884/helping-the-others-realize-the-advantages-of-bip39-mnemonic-phrase-tool