For words that have only 3 letters, there isn't a 4th letter. One example is with the word “incorporate”, there are no more letters afterwards and therefore needs to be the word "incorporate". The word “addict” is within the BIP39 wordlist however , you would've employed “addi” for “addict”. Meticulously https://bookmarkity.com/story18908514/facts-about-bip39-seed-phrase-github-revealed