concrete

Real, actual, tangible.

Analogous to the categories of algebraic objects which category theory was created to generalize, in the sense of having objects which can be thought of as sets equipped with some additional structure. Formally, equipped with a faithful functor to the category of sets.

Equipped with a faithful functor to X (called a base category), in which case C is called a concrete category over X.

Being or applying to actual things, rather than abstract qualities or categories.

Particular, specific, rather than general.

Made of concrete (building material).

Made up of separate parts; composite.

Not liquid or fluid; solid.