For words that only have 3 letters, there is absolutely no 4th letter. As an example with the word “add”, there won't be any extra letters Later on and therefore should be the word "add". The word “addict” is during the BIP39 wordlist however , you would've employed “addi” for https://top100bookmark.com/story19775803/helping-the-others-realize-the-advantages-of-bip39-seed-phrase-mnemonics-generator