linguistic:translation, structural:expansion
Classification

In hydrology, a stream order is a positive integer used to describe the level of river branching in a drainage basin. Several systems of stream order exist, one of which is the Strahler number. In this system, the first tributaries of a river are 1st order rivers. When two 1st order rivers merge, the resulting river is 2nd order. If a river of a higher order and a lower order merge, the order is incremented from whichever of the previous rivers had the higher order. Stream order is correlated with and thus can be used to predict certain data points related to rivers, such as the size of the drainage basin (drainage area), and the length of the channel.