For words that only have 3 letters, there's no 4th letter. Such as with the word “increase”, there aren't any additional letters Later on and so need to be the word "insert". The word “addict” is within the BIP39 wordlist but you would've utilized “addi” for “addict”. Mnemonic words illustrations https://bookmarktune.com/story18933773/top-latest-five-bip39-words-urban-news