Nodal Analysis & Identifying Nodes
TL;DR Nodes are the wires on schematics, not the dots.

In circuit analysis, a node is a collection of points, at the same voltage, connected by ideal wires, that can be treated as a single point for all purposes.

That means that these ideal wires have zero resistance, zero inductance, zero capacitance to anything else, and zero electrical length.

In the case of your diagram, there is a single node connecting the bottom of iA, R1, iB and R3. This is indicated by the fact that that connection is drawn as an ideal wire. 

The multiple connection dots on that node are a drawing convenience. We generally find that drawings restricted to vertical and horizontal wires are tidier and easier to read than if wires take other angles, which a single dot for this node would entail.