Narrow gauge railways

The strict definition of a narrow gauge railway is any railway with a gauge (the distance between the rails) that is less than 'standard gauge' - 1,435 mm or 4'8½".  There are various 'standards' of narrow gauge - ranging from the not-very-narrow 1,372 mm or 4' 6" to perhaps the narrowest narrow gauge of 600 mm or 1' 11⅝", which is effectively interchangeable with the fairly common 'two-foot' or 610 mm gauge.

In general, any narrower gauge, such as the 7¼" gauge Beer Heights Light Railway at Pecorama in Beer, England, is a model representing a wider (usually standard) gauge prototype.