For words that have only 3 letters, there is absolutely no 4th letter. By way of example with the word “increase”, there won't be any additional letters afterwards and thus should be the word "add". The word “addict” is during the BIP39 wordlist however you might have utilized “addi” for https://fellowfavorite.com/story20016172/5-simple-techniques-for-bip39-seed-phrase