For words that have only three letters, there's no 4th letter. For example with the word “increase”, there won't be any much more letters Later on and thus have to be the word "add". The word “addict” is during the BIP39 wordlist however you would've applied “addi” for “addict”. bip39-phrase.com https://social-lyft.com/story8700173/detailed-notes-on-copyright-wallet-seed-phrase-out-of-bip39