For words that have only three letters, there is absolutely no 4th letter. By way of example with the word “add”, there are no far more letters afterwards and thus must be the word "incorporate". The word “addict” is in the BIP39 wordlist however, you might have utilized “addi” for https://pageoftoday.com/story4411670/the-2-minute-rule-for-bip39-all-words