For words that have only three letters, there is no 4th letter. For example with the word “increase”, there won't be any much more letters Later on and so need to be the word "include". The word “addict” is in the BIP39 wordlist however, you might have made use of https://bookmark-group.com/story4368670/how-much-you-need-to-expect-you-ll-pay-for-a-good-valid-bip39-seed-phrase