1. A phrase used to emphasize the negation or absence of something, often introducing an additional negative point to strengthen an argument
He didn't apologize, and he didn't even acknowledge his mistake.
Ele não se desculpou, e nem sequer reconheceu seu erro.
2. Used to express surprise or disappointment that something minimal or expected did not occur
She left without saying goodbye, and she didn't even send a message.
Ela saiu sem se despedir, e nem sequer enviou uma mensagem.