For words that only have three letters, there isn't any 4th letter. Such as with the word “add”, there won't be any much more letters Later on and so have to be the word "include". The word “addict” is while in the BIP39 wordlist however , you would've employed “addi” https://pageoftoday.com/story4237715/5-simple-techniques-for-bip39-seed-phrase