For words that have only three letters, there isn't any 4th letter. For example with the word “add”, there are no more letters Later on and thus have to be the word "include". The word “addict” is during the BIP39 wordlist however you would've employed “addi” for “addict”. Safety: Anyone https://checkbookmarks.com/story4386978/the-definitive-guide-to-bip39-seed-phrase