Triangle ABC: Analyzing Side DB and Point Relationships

Let us determine whether $DB$ is a side of triangle $ABC$. This verification depends greatly on understanding the arrangement and positioning of the points given within the triangle.

From the diagram, points $A$, $B$, and $C$ form a triangle because they create a closed figure with three lines connecting one another, typical of triangle sides. On examining point $D$ and the line $DB$, we notice that $D$ seems to be an internal point, potentially serving roles like that of a median or an angle bisector, but not forming an external side of triangle $ABC$.

Based on this understanding, line $DB$ fails to fulfil the requirement of connecting two of the vertices of the triangle directly. Hence, it's internal and is not counted as an external side of triangle $ABC$.

The conclusion based on the given options from the prompt: $DB$ is not a side of triangle $ABC$.