For words that only have 3 letters, there is no 4th letter. For example with the word “incorporate”, there are no much more letters Later on and therefore should be the word "add". The word “addict” is while in the BIP39 wordlist however, you might have utilized “addi” for “addict”. https://social-medialink.com/story4086831/a-review-of-bip39-phrase-list