For words that only have three letters, there isn't a 4th letter. Such as with the word “include”, there are no additional letters afterwards and therefore have to be the word "add". The word “addict” is from the BIP39 wordlist but you might have made use of “addi” for “addict”. https://minibookmarks.com/story18808765/top-latest-five-bip39-words-urban-news