For words that only have 3 letters, there's no 4th letter. Such as with the word “add”, there won't be any a lot more letters afterwards and therefore should be the word "include". The word “addict” is from the BIP39 wordlist but you might have used “addi” for “addict”. Standard https://linkingbookmark.com/story18728364/not-known-facts-about-bip39-english-words