For words that have only 3 letters, there is absolutely no 4th letter. For instance with the word “increase”, there won't be any much more letters Later on and therefore should be the word "increase". The word “addict” is while in the BIP39 wordlist but you would've made use of https://techonpage.com/story4183296/invalid-bip39-phrase-things-to-know-before-you-buy