Definition:Object (Category Theory)
Let $\mathbf C$ be a metacategory.
It is a conceptual device introduced mainly to make the discussion of morphisms more convenient.
Objects in a general metacategory are usually denoted with capital letters like $A,B,C,X,Y,Z$.
The collection of objects of $\mathbf C$ is denoted $\mathbf C_0$.
That objects don't play an important role in category theory is apparent from the fact that the notion of a metacategory can be described while avoiding to mention objects altogether.