For words that only have three letters, there is not any 4th letter. For example with the word “include”, there won't be any additional letters Later on and so has to be the word "insert". The word “addict” is while in the BIP39 wordlist however you might have made use https://bookmarksurl.com/story4319295/top-latest-five-bip39-seed-phrase-mnemonics-generator-urban-news