For words that only have 3 letters, there is no 4th letter. For example with the word “incorporate”, there aren't any far more letters afterwards and so have to be the word "increase". The word “addict” is during the BIP39 wordlist but you would have used “addi” for “addict”. Stability: https://worldsocialindex.com/story4128670/top-latest-five-bip39-words-urban-news