For words that have only three letters, there's no 4th letter. For example with the word “include”, there aren't any a lot more letters Later on and so need to be the word "add". The word “addict” is from the BIP39 wordlist however you might have employed “addi” for “addict”. https://thekiwisocial.com/story4257779/facts-about-bip39-seed-phrase-word-list-revealed