Maximum means the greatest amount, level, or degree that something can reach or that is allowed. When a sign says “Maximum capacity: 50 people,” it means the room can hold no more than 50 people safely. When you're driving and see “Maximum speed: 65 mph,” that's the fastest you're legally allowed to go.

Scientists use maximum to describe the highest point something reaches: the maximum temperature today might be 85 degrees, meaning it won't get any hotter than that. A bridge might have a maximum weight limit of 10 tons, meaning heavier trucks would risk damaging it.

Sometimes people use maximum informally to mean “the most possible,” as in “I'm putting in maximum effort” or “Turn the music up to maximum volume!” The opposite of maximum is minimum, which means the smallest or least amount.

You might also see the informal short form max, as in “I can stay for two hours, max,” meaning two hours is the absolute most time available. When you've maxed out something, like maxing out your screen time for the day, you've reached the maximum limit and can't have any more.