A loop (or mesh is any closed path through the circuit in which nodes appear at most once. Meshes are defined in planar circuits, which are circuits that can be drawn on a plane surface with no wires crossing each other. Loops are slightly more general and can be applied to any circuit, planar or not. Since all the electric circuits that appear on this website are planar we will use mesh and loop interchangeably.

The outside mesh of a circuit is the largest mesh in the circuit; a minor mesh (also called essential mesh) is a mesh that does not contain any other meshes.

A circuit can have multiple loops (or meshes). For instance, the circuit shown in Fig. 1 has 3 minor meshes labeled $i_1$, $i_2$, and $i_3$ and the outside mesh. Since, we are almost always interested only in the minor meshes and the outside mesh, we will simply say that that the circuit below contains 3 meshes (or 3 loops) plus the outside mesh (or outside loop).

Loops and meshes are made of branches.

Any circuit should contain at least 1 mesh. When the circuit contains only 1 mesh (excluding the outside mesh), it is called single loop circuit (see Fig. 2).

Mesh analysis is a method based on Kirchhoff’s Voltage Law (KVL) that can be used to analyze planar electric circuits. Loop analysis is slightly more general and can be applied to non-planar circuits. Mesh analysis is usually easier to use than loop analysis because the circuit is planar. However, notice again that, since the electric circuits on this site are planar, we will use mesh analysis and loop analysis interchangeably.