For words that only have three letters, there isn't a 4th letter. As an example with the word “add”, there isn't any far more letters Later on and therefore should be the word "incorporate". The word “addict” is in the BIP39 wordlist but you might have utilized “addi” for “addict”. https://thesocialvibes.com/story4333000/the-invalid-bip39-phrase-diaries