What is the difference between viaduct and bridge?

Viaducts are types of bridges; the term “viaduct” refers to long bridges or series of bridges that are connected to one another or structurally supported by arches or sturdy platforms between two end towers. As with bridges, viaducts may cross waterways or roadways, and exist primarily to provide an overhead passage to move trucks, cars, trains and pedestrians from one point to another.