For words that only have 3 letters, there isn't a 4th letter. For example with the word “add”, there won't be any far more letters Later on and therefore must be the word "add". The word “addict” is during the BIP39 wordlist however, you would've utilised “addi” for “addict”. Standard https://webnowmedia.com/story5016488/considerations-to-know-about-bip39-seed-phrase-generator