Triangle Side AB: Identifying Line Segments Between Two Similar Triangles

To solve this problem, we will inspect the two triangles in the diagram to determine if $AB$ can be identified as one of their sides.

1. We begin by examining the triangle on the left side, which is formed by points $A$, $B$, and $C$.
- Point $A$ is located at the top of the triangle, while point $B$ is at the bottom left.
- The diagram clearly shows a direct line connecting point $A$ to point $B$, therefore forming a side of this triangle.

2. There is another triangle on the right side of the diagram formed by points $D$, $E$, and $F$. However, since points $A$ and $B$ are not involved in this triangle, they cannot form a side of it.

Hence, it is evident that $AB$ is indeed a side of the left triangle, comprising points $A$, $B$, and $C$.

Therefore, the answer to the problem is Yes.