For words that have only three letters, there's no 4th letter. Such as with the word “include”, there are no extra letters Later on and thus must be the word "add". The word “addict” is during the BIP39 wordlist however , you would have used “addi” for “addict”. Artwork is https://socialmphl.com/story20916771/how-much-you-need-to-expect-you-ll-pay-for-a-good-bip39-definition