depth

Depth is a measure of how far something lies below a surface or reference plane. It denotes distance downward or inward from the outermost boundary, and it can apply to liquids, solids, and abstract spaces.

In bodies of water, depth is the distance from the surface to the bottom. It is commonly expressed in meters or feet and mapped through bathymetry using sonar or echo sounding.

Depth perception is the visual system’s ability to judge distance and three-dimensional structure. It relies on cues such as binocular disparity, motion parallax, perspective, texture gradient, and shading. In photography and optics, depth of field describes the range of sharp focus in an image along the depth axis.

In computer science and mathematics, depth often refers to the length of the longest path from a starting point to a terminal point. For a tree data structure, depth is the maximum number of edges from the root to a leaf. In recursion, recursion depth is the level of nested calls.

In geology and geography, depth can denote the thickness of a buried layer or the vertical distance from the surface to a geological feature.

In humanities and everyday language, depth is used to describe complexity, significance, or richness beyond surface appearance. It can signal a thorough understanding, substantial meaning, or nuanced interpretation.