For words that have only 3 letters, there is absolutely no 4th letter. For example with the word “add”, there isn't any additional letters afterwards and therefore should be the word "include". The word “addict” is within the BIP39 wordlist however, you would've employed “addi” for “addict”. Try to be https://bookmarkstumble.com/story20456722/not-known-facts-about-bip39-english-words