For words that only have 3 letters, there is no 4th letter. Such as with the word “insert”, there aren't any extra letters afterwards and thus needs to be the word "incorporate". The word “addict” is inside the BIP39 wordlist however you would've utilized “addi” for “addict”. Acquiring a single https://socialtechnet.com/story4324710/bip39-phrase-generator-can-be-fun-for-anyone