Uh is a sound people make when they're thinking, hesitating, or unsure what to say next. When your teacher calls on you unexpectedly and you need a moment to gather your thoughts, you might start with “Uh, I think the answer is...” When you're trying to remember someone's name or searching for the right word, an uh often fills the gap.

These sounds are called filler words or hesitation sounds, and many people use them, even professional speakers and teachers. They buy your brain a split second to catch up with your mouth. You might say “Uh, can you repeat the question?” or “Uh, I'm not sure about that.”

Some people say uh more than others, especially when nervous or speaking about something complicated. While occasional uhs are perfectly normal in conversation, a lot of them can make you sound uncertain or unprepared. When you're giving a presentation, practicing beforehand can reduce those uhs because you already know what you want to say.

The word um works similarly to uh, though uh tends to be shorter and quicker.