For words that only have 3 letters, there is absolutely no 4th letter. For instance with the word “incorporate”, there are no a lot more letters Later on and therefore should be the word "increase". The word “addict” is within the BIP39 wordlist however you would've applied “addi” for “addict”. https://bbsocialclub.com/story20667144/examine-this-report-on-bip39-mnemonic-phrase-tool