For words that have only 3 letters, there isn't a 4th letter. One example is with the word “incorporate”, there aren't any extra letters Later on and therefore have to be the word "incorporate". The word “addict” is within the BIP39 wordlist however, you might have utilized “addi” for “addict”. https://thebookmarkfree.com/story19595781/bip39-phrase-generator-can-be-fun-for-anyone