deep

Deep is a common English word that functions as an adjective and, less frequently, as a noun. It derives from Old English deop and is related to the noun depth.

In everyday language it denotes distance from a surface or thoroughness and intensity. It is used for both physical depth—deep water, deep caves, the deep sea—and abstract notions such as deep thought, deep emotion, or deep color. The term can carry connotations of complexity or profundity in discussion, art, and culture.

In science and technology, deep often signals layered structure or advanced abstraction. Deep learning, a major subfield of artificial intelligence, uses neural networks with many layers to model complex patterns from large data sets. In information technology, the deep web refers to parts of the Internet not indexed by standard search engines, including databases and password-protected sites, distinct from the surface web.

As a personal name, Deep is used in South Asia, typically conveying the idea of light or lamp. It appears in given names such as Deep and Deepak. The term also appears in music genres (for example, deep house) and in literary or academic phrases such as deep structure, signaling a foundational or underlying level of organization.

Because of its broad usage, the exact meaning of deep depends on context, ranging from measurements of physical depth to considerations of conceptual depth and complexity.