For words that only have three letters, there's no 4th letter. As an example with the word “add”, there won't be any a lot more letters Later on and thus must be the word "insert". The word “addict” is inside the BIP39 wordlist however , you would have applied “addi” https://dailybookmarkhit.com/story18882220/the-fact-about-bip39-seed-phrase-word-list-that-no-one-is-suggesting