For words that only have three letters, there is not any 4th letter. For instance with the word “insert”, there won't be any a lot more letters Later on and therefore has to be the word "increase". The word “addict” is within the BIP39 wordlist but you would've applied “addi” https://pr7bookmark.com/story19253633/how-much-you-need-to-expect-you-ll-pay-for-a-good-bip39-definition