For words that only have three letters, there is no 4th letter. Such as with the word “incorporate”, there aren't any additional letters Later on and so need to be the word "incorporate". The word “addict” is during the BIP39 wordlist however, you might have utilized “addi” for “addict”. Multiple https://listfav.com/story20282198/little-known-facts-about-bip39-words