For words that only have three letters, there is absolutely no 4th letter. Such as with the word “add”, there isn't any far more letters afterwards and so have to be the word "include". The word “addict” is during the BIP39 wordlist however , you might have used “addi” for https://toplistar.com/story20644365/facts-about-bip39-seed-phrase-word-list-revealed