For words that have only 3 letters, there is not any 4th letter. Such as with the word “increase”, there are no extra letters afterwards and thus should be the word "include". The word “addict” is in the BIP39 wordlist however, you might have utilised “addi” for “addict”. BIP39 and https://madbookmarks.com/story18823364/fascination-about-bip39-english-words