For words that only have three letters, there is absolutely no 4th letter. For example with the word “add”, there isn't any a lot more letters Later on and thus have to be the word "include". The word “addict” is in the BIP39 wordlist however, you would've utilised “addi” for https://alphabookmarking.com/story18843804/the-fact-about-valid-bip39-seed-phrase-that-no-one-is-suggesting