There isn't a single universally accepted classification of landforms into only three types. However, a common way to broadly categorize them is based on their origin or dominant process:

1. Erosional Landforms: These are shaped primarily by the removal of material, such as weathering, erosion, and transportation. Examples include:

* Canyons: Deep, narrow valleys carved by rivers.

* Sea Cliffs: Steep rock faces formed by wave erosion.

* Sand Dunes: Formed by wind deposition and erosion of sand.

* U-shaped Valleys: Formed by glacial erosion.

2. Depositional Landforms: These are formed by the accumulation of material, often transported by water, wind, or ice. Examples include:

* Deltas: Areas where rivers deposit sediment as they enter a larger body of water.

* Alluvial Fans: Cone-shaped deposits of sediment at the base of mountains.

* Moraines: Ridges of rock and sediment deposited by glaciers.

* Sandbars: Elongated deposits of sand in rivers or along coastlines.

3. Structural Landforms: These are formed by tectonic activity and geological processes that create large-scale structures in the Earth's crust. Examples include:

* Mountains: Formed by the uplifting of the Earth's crust.

* Volcanoes: Cones formed by the eruption of lava and ash.

* Plateaus: Elevated areas of relatively flat land.

* Faults: Fractures in the Earth's crust where movement has occurred.

It's important to note that these categories can sometimes overlap, and many landforms are a product of multiple processes. For example, a mountain range may be initially formed by tectonic activity, but then shaped by erosion.