For words that only have three letters, there is no 4th letter. For example with the word “incorporate”, there aren't any extra letters afterwards and so must be the word "increase". The word “addict” is from the BIP39 wordlist but you would've applied “addi” for “addict”. Finding one missing word https://atozbookmark.com/story19348023/the-ultimate-guide-to-bip39-seed-phrase-mnemonics-generator