For words that have only 3 letters, there isn't a 4th letter. One example is with the word “incorporate”, there isn't any far more letters afterwards and so should be the word "insert". The word “addict” is inside the BIP39 wordlist however , you would've employed “addi” for “addict”. A https://friendlybookmark.com/story18749946/bip39-seed-phrase-fundamentals-explained