For words that have only three letters, there isn't a 4th letter. One example is with the word “insert”, there won't be any a lot more letters Later on and therefore need to be the word "incorporate". The word “addict” is inside the BIP39 wordlist but you would've applied “addi” https://topsocialplan.com/story4511362/the-ultimate-guide-to-bip39-seed-phrase-github