For words that have only 3 letters, there isn't a 4th letter. As an example with the word “insert”, there won't be any a lot more letters Later on and thus should be the word "increase". The word “addict” is while in the BIP39 wordlist but you might have made https://onelifesocial.com/story4153998/the-2-minute-rule-for-bip39-all-words