For words that have only three letters, there isn't a 4th letter. One example is with the word “incorporate”, there are no far more letters afterwards and therefore needs to be the word "incorporate". The word “addict” is from the BIP39 wordlist but you would've applied “addi” for “addict”. Discovering https://redhotbookmarks.com/story18863643/little-known-facts-about-bip39-words