For words that only have three letters, there isn't a 4th letter. As an example with the word “add”, there won't be any far more letters Later on and thus have to be the word "incorporate". The word “addict” is in the BIP39 wordlist however you would've applied “addi” for https://mylittlebookmark.com/story4462591/considerations-to-know-about-bip39-word-list-pdf