For words that have only three letters, there is absolutely no 4th letter. For instance with the word “increase”, there won't be any much more letters Later on and thus needs to be the word "incorporate". The word “addict” is within the BIP39 wordlist but you might have made use https://bookmarknap.com/story9034709/how-much-you-need-to-expect-you-ll-pay-for-a-good-bip39-seed-phrase-mnemonics-generator