For words that have only three letters, there is not any 4th letter. For instance with the word “increase”, there isn't any much more letters afterwards and therefore has to be the word "add". The word “addict” is within the BIP39 wordlist however you would've made use of “addi” for https://bookmarkgenious.com/story19150691/little-known-facts-about-bip39-seed-phrase-list