For words that only have three letters, there isn't a 4th letter. For example with the word “insert”, there isn't any much more letters afterwards and therefore should be the word "include". The word “addict” is from the BIP39 wordlist but you would have utilized “addi” for “addict”. Artwork is https://mirrorbookmarks.com/story19078428/not-known-facts-about-bip39-english-words