What does deep mean?
"Deep" is one of English's oldest and most versatile words, describing anything that extends far downward, inward, or backward from its surface or edge — a deep well, a deep cut, a deep forest. Beyond the physical sense, it carries rich figurative weight: emotions can be deep, thoughts can be deep, and a person's knowledge or a problem's difficulty can be described the same way. It also applies to sensory qualities, as in a deep voice or a deep blue color, where it suggests richness or low intensity of pitch. As a noun, "the deep" is a poetic name for the open sea. The word appears constantly in fixed expressions like "take a deep breath," "in deep water," and "deep down," and it forms a productive family including "depth," "deepen," and "deeply." Few adjectives span so naturally between the tangible and the abstract, which is why "deep" remains indispensable in everyday speech and literature alike.
Extending far downward or inward from the surface or edge; also profound, intense, or low-pitched by extension.
"The trench is the deepest part of the ocean."
Figurative uses (deep sorrow, deep insight) are as common today as literal ones.
To a great depth or distance; far down or far in.
"The ship sank deep beneath the waves."
The deepest or most remote part of something; especially (the deep) the open sea.
"Legends told of creatures rising from the deep."
Rare and mostly literary; usually found as "the deeps" referring to vast expanses of sea, sky, or space.
"The poem evokes the silent deeps of outer space."
English borrowed almost nothing to build its vocabulary of depth — "deep," "dip," and "depth" all come from the same ancient root our language has carried for thousands of years.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of deep
"Deep" descends from Old English "dēop," tracing back through Proto-Germanic to an ancient root shared across the Germanic family. Its closest relatives include Dutch "diep" and German "tief," while the verb "dip" comes from the same ancestral source. Unlike much of English vocabulary, it was never replaced by a Latin or French borrowing, preserving a direct line to the earliest strata of the language.
Related word forms
How deep is actually used
"Deep" works both literally (physical distance) and figuratively (emotional or intellectual profundity), which makes it one of English's most flexible adjectives. In informal speech it can even mean emotionally absorbed, as in "he was deep in thought." The adverb form "deep" ("they went deep into the woods") coexists with "deeply"; "deep" tends to appear with verbs of motion.
Easily confused with deep
"Dep" is only an informal abbreviation (e.g. for deposit or departure), while "deep" is the full adjective meaning far down or profound.