For words that have only 3 letters, there isn't any 4th letter. Such as with the word “include”, there won't be any a lot more letters Later on and thus needs to be the word "include". The word “addict” is inside the BIP39 wordlist however you would've applied “addi” for https://allkindsofsocial.com/story4279878/the-2-minute-rule-for-bip39-all-words