A tensor network is a graph with one tensor at each vertex. Every edge, called a wire, carries one bit shared by its two endpoints. Each endpoint assigns that edge to a particular port of its tensor, so port order matters. Distinct parallel edges carry distinct bits, even though they join the same vertices. Vertex degree is its number of incident wires. A bipartite network separates vertices into two sides, with every edge crossing between sides. An isolated vertex has no wires and contributes its scalar entry. Network size here counts wires, not the number of possible global bit assignments.