What's the "een" in Halloween?
erosion e·ro·sion (ĭ-rō'zhən)
Superficial destruction of a surface by friction, pressure, ulceration, or trauma.
The wearing away of a tooth by chemical or abrasive action. Also called odontolysis.
The gradual wearing away of land surface materials, especially rocks, sediments, and soils, by the action of water, wind, or a glacier. Usually erosion also involves the transport of eroded material from one place to another, as from the top of a mountain to an adjacent valley, or from the upstream portion of a river to the downstream portion.