For words that have only 3 letters, there is no 4th letter. Such as with the word “incorporate”, there aren't any much more letters afterwards and therefore needs to be the word "add". The word “addict” is during the BIP39 wordlist however, you might have applied “addi” for “addict”. bip39-phrase.com https://freshbookmarking.com/story18876346/helping-the-others-realize-the-advantages-of-bip39-mnemonic-phrase-tool