For words that only have 3 letters, there isn't a 4th letter. By way of example with the word “include”, there are no far more letters Later on and thus must be the word "insert". The word “addict” is within the BIP39 wordlist however, you would have applied “addi” for https://socialfactories.com/story4250269/a-review-of-bip39-phrase-list