River (typography)

Broader typefaces are more prone to exhibit rivers, as are the less sophisticated typesetting applications that offer little control over spacing.

A carefully composed text page appears as an orderly series of strips of black separated by horizontal channels of white space.

Conversely, in a slovenly setting the tendency is for the page to appear as a grey and muddled pattern of isolated spats, this effect being caused by the over-widely separated words.

The eye also tends to be confused by a feeling of vertical emphasis, that is, an up & down movement, induced by the relative isolation of the words & consequent insistence of the ascending and descending letters.

Other related terms are lakes and holes, which refer to a cluster of adjacent or intertwined rivers that create a lighter area within a block of type.