For words that only have three letters, there is no 4th letter. Such as with the word “insert”, there aren't any a lot more letters Later on and therefore has to be the word "incorporate". The word “addict” is within the BIP39 wordlist however you would've utilized “addi” for “addict”. https://bookmark-vip.com/story18880757/how-much-you-need-to-expect-you-ll-pay-for-a-good-valid-bip39-seed-phrase