For words that have only 3 letters, there's no 4th letter. Such as with the word “increase”, there are no more letters afterwards and so need to be the word "include". The word “addict” is from the BIP39 wordlist but you would have utilised “addi” for “addict”. To test to https://health-lists.com/story19462419/not-known-facts-about-bip39-english-words