For words that only have three letters, there's no 4th letter. Such as with the word “increase”, there aren't any extra letters afterwards and thus has to be the word "incorporate". The word “addict” is from the BIP39 wordlist however, you would have applied “addi” for “addict”. A seed phrase, https://admiralbookmarks.com/story19053166/helping-the-others-realize-the-advantages-of-bip39-mnemonic-phrase-tool