For words that have only 3 letters, there's no 4th letter. Such as with the word “include”, there aren't any additional letters Later on and therefore need to be the word "incorporate". The word “addict” is while in the BIP39 wordlist however, you would've applied “addi” for “addict”. The way https://onelifesocial.com/story4134556/the-definitive-guide-to-bip39-seed-phrase