For words that have only three letters, there is no 4th letter. For instance with the word “add”, there are no a lot more letters afterwards and so need to be the word "incorporate". The word “addict” is inside the BIP39 wordlist however you might have utilised “addi” for “addict”. https://bookmarkbooth.com/story19008973/examine-this-report-on-bip39-mnemonic-phrase-tool