What type of defect is classified as one-sided?

A crater is classified as a one-sided defect due to its specific formation and characteristics. Craters are typically observed as round depressions on a surface, appearing as a result of localized degradation or material loss. Unlike more complex shapes, craters have a defined rim and a depth which only extends in one direction, making them unidimensional in nature.

Other types of defects, such as trenches or moats, generally exhibit features that involve a larger area or more complex boundaries, which do not conform to the characteristics of a one-sided defect. Trenches are elongated and can involve more than just a single plane, while moats often possess a defined perimeter or a multi-sided aspect. A pocket, likewise, implies a more voluminous defect that does not adhere to the concept of being one-sided. Therefore, the uniqueness of the crater’s shape and structure qualifies it as the correct answer in this context.