In the United States, a mountain is 1,000 feet (304.4 metres) or more in height from bottom to summit. A hill is 500 (152.4 metres) to 999 (304 metres) feet. A discernible hill that is less than 500 feet high is a knoll. A series of knolls constitutes a rolling plain. A plain is generally considered flat if it has no significant prominences (e.g., "hills" less than 20 feet high, though the range of height varies for a plain to be considered flat).[
citation needed]
United Kingdom
In
England and Wales the
Department for Environment, Food and Rural Affairs has defined "mountain" (as a
mass noun) as all land over 600 metres, for the purposes of
right to roam legislation. This is a close metric equivalent of 2,000 feet (609.6 m).
[4] The
Land Reform (Scotland) Act 2003 does not appear to draw this distinction, and in
Scotland the term "mountain" is more subjective, often being used for hills exceeding 3,000 feet (914.4 m) listed as
Munros, as well as many lower hills which are distinctive or mountainous. In the United Kingdom the term "hill" is commonly used for all hills and mountains, regardless of height.