Answer : The abstract noun for deep is Depth.
It is common practice to use an abstract noun when referring to things that cannot be heard, seen, tasted or felt. In contrast to concrete nouns, abstract nouns lack substance. A significant number of proverbs make use of intangible nouns.
An abstract noun is “a noun, for example, beauty or freedom, that refers to an idea or a general quality, and not to a physical object,” as defined by the Oxford Learners Dictionary. An abstract noun is a noun that does not refer to a concrete thing but rather to an idea or a quality,
So the answer is Depth.