Re: How high does a mountain have to be to be a mountain and not a hill?

Sometimes terms do not have exact definitions, or have slightly different definitions for different purposes or in different countries. There is not a recognised, all-purpose definition that separates hills from mountains. I know of many "mountains" that are less than 500 metres above sea-level, and many "hills" that are more than 1000 metres above sea-level.

Generally mountains are higher than hills. But sometimes mountains are more rugged than hills, which are thought of as gentler and smoother. Context can be important: height above a surrounding plateau may be more important than height above sea-level. Or whether a feature is in a generally rugged region, or a single feature that stands out above a plain. Hills in New Zealand are much larger than mountains in Australia, because their country is nearly all very rugged and mountainous, with quite high peaks, while ours has huge areas of plain, nothing really high, and only small regions that are rugged.