For words that have only three letters, there isn't any 4th letter. By way of example with the word “add”, there are no a lot more letters afterwards and thus has to be the word "increase". The word “addict” is from the BIP39 wordlist however you would've used “addi” for https://bookmarkzap.com/story18720061/not-known-facts-about-bip39-english-words