For words that have only 3 letters, there's no 4th letter. For example with the word “add”, there won't be any more letters Later on and so should be the word "increase". The word “addict” is within the BIP39 wordlist however you would've made use of “addi” for “addict”. Artwork https://social-medialink.com/story4188772/how-much-you-need-to-expect-you-ll-pay-for-a-good-bip39-seed-phrase-mnemonics-generator