No one means not a single person, absolutely nobody. When you say no one showed up to your party, you mean that zero people came. When a teacher asks who forgot their homework and no one raises their hand, every single student completed the assignment.

The phrase works as the opposite of “everyone” or “someone.” If everyone knows the answer, that means all people know it. If someone knows the answer, at least one person does. But if no one knows the answer, not a single person has figured it out.

You'll often see no one paired with negative situations: No one likes being left out. No one wants to lose. No one enjoys getting sick. But it can describe positive situations too: No one got hurt in the accident. No one failed the test.

The phrase captures a complete absence of people in a clear, definitive way. When you say no one, you mean exactly what you say.