For words that only have three letters, there isn't any 4th letter. Such as with the word “incorporate”, there won't be any much more letters Later on and thus have to be the word "include". The word “addict” is in the BIP39 wordlist however , you might have applied “addi” https://linkedbookmarker.com/story5130201/getting-my-bip39-words-to-numbers-to-work