How tall must a mountain be to be called a mountain?

Answer 1

I believe it's not height but how it was formed. Take for example Mt. Everest and the surrounding mountains. This mountain is created as the two continental plated push up against each other. This cause the Earth that meets between these two plates to push up.

Answer 2

There is no set height requirement for a landform to be considered a mountain, but traditionally, a mountain is often defined as having an elevation of at least 1,000 feet (300 meters) above its surroundings. Other factors, such as steepness and prominence, can also contribute to classifying a landform as a mountain.