For words that only have three letters, there isn't a 4th letter. As an example with the word “add”, there isn't any far more letters Later on and so need to be the word "increase". The word “addict” is within the BIP39 wordlist however , you might have applied “addi” https://bookmarkingace.com/story18799752/how-much-you-need-to-expect-you-ll-pay-for-a-good-bip39-definition