For words that have only 3 letters, there's no 4th letter. As an example with the word “increase”, there won't be any far more letters afterwards and thus must be the word "incorporate". The word “addict” is within the BIP39 wordlist but you would have utilised “addi” for “addict”. A https://thebookmarklist.com/story18978332/examine-this-report-on-bip39-passphrase