rillen

Rillen is the plural form of the German noun Rille and is used in other languages to denote long, narrow depressions or channels on a surface. The term covers natural grooves as well as man-made grooves and is used in geology, astronomy and engineering.

In geology and geomorphology, rillen refer to grooves or channels formed by erosion, weathering, or glacial action in rock, soil, or sediment. They range from small soil rills on slopes to larger bedrock channels and can occur in deserts, valleys, and coastal areas.

In astronomy, rille (plural rillen) designates a lunar feature: a narrow channel or trough on the Moon. Rilles are categorized as straight, sinuous, or arcuate. Straight rilles are fault-related or lava-filled trenches; sinuous rilles resemble winding river valleys; arcuate rilles are curved remnants near crater rims.

In engineering and materials science, rillen describe grooves produced by cutting, wear, or abrasion. Such grooves affect surface properties such as friction, lubrication, and light interaction, and they are relevant in manufacturing, tire design, and road surfaces.

Etymology and usage: The term derives from German Rille, meaning groove or furrow. While common in German-language technical writing, rillen appears in English primarily when referring to lunar rilles or in technical translations that use the German term.