For words that have only three letters, there isn't any 4th letter. By way of example with the word “insert”, there isn't any much more letters afterwards and thus has to be the word "incorporate". The word “addict” is during the BIP39 wordlist but you would have used “addi” for https://yourbookmarklist.com/story19192171/examine-this-report-on-bip39-mnemonic-phrase-tool