For words that only have three letters, there isn't a 4th letter. One example is with the word “add”, there aren't any a lot more letters afterwards and so needs to be the word "include". The word “addict” is in the BIP39 wordlist however , you might have made use https://mysitesname.com/story8792718/how-much-you-need-to-expect-you-ll-pay-for-a-good-bip39-definition