For words that only have 3 letters, there isn't any 4th letter. Such as with the word “insert”, there won't be any extra letters afterwards and thus needs to be the word "include". The word “addict” is within the BIP39 wordlist but you would have made use of “addi” for https://telebookmarks.com/story9290764/the-fact-about-bip39-seed-phrase-word-list-that-no-one-is-suggesting