What characteristic defines a line feature?

A line feature in geographic information systems is defined by two or more connected vertices. This characteristic allows for the representation of linear data, such as roads, rivers, or pathways, where the connection between the vertices creates a continuous path. Each vertex serves as a point defining the shape and direction of the line feature.

The other choices describe different geometric features. Three or more connected vertices creating a closed ring would define a polygon, which is a closed shape rather than a linear one. A single vertex does not form any feature by itself, as it lacks length or connectivity. Lastly, three or more vertices can represent a line or polygon depending on the arrangement, but they do not specifically define the linear nature without connecting them in a two-point system. The crucial element for a line feature is its linear continuity facilitated by at least two vertices.