A landform comprises a geomorphological unit. Oceans and continents exemplify highest-order landforms.
A number of factors, ranging from plate tectonics to erosion and deposition can generate and affect landforms. Biological factors can also influence landforms -- see for example the role of plants in the development of dune systems and salt marshes, and the work of corals and algae in the formation of coral reefs.
See also: geomorphology, topography, physical geography, earth science.
Landforms produced by erosion and weathering usually occur in coastal or fluvial environments, and many appear above under those headings. Some other erosion landforms that do not fall into the above categories include: