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.

A minor mesh (or minor loop) is a mesh that does not contain any other meshes. The outside mesh (or outside loopof a circuit includes all the minor meshes in the circuit and is usually considered as a reference mesh.

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 one mesh. When the circuit contains only one mesh (which is the same as the outside mesh), it is called single loop circuit (see Fig. 2).

Mesh analysis is a method based on Kirchhoff's voltage law 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 all the electric circuits on this website are planar, we will use the names mesh analysis and loop analysis interchangeably.