For words that have only three letters, there is no 4th letter. Such as with the word “add”, there isn't any a lot more letters Later on and therefore needs to be the word "incorporate". The word “addict” is from the BIP39 wordlist however you would've employed “addi” for “addict”. https://www.storeboard.com/blogs/beauty-and-fashion/opening-the-globe-of-bip39-a-comprehensive-guide-to-mnemonic-expressions-and-word-checklists/6026188