## Definition

A region is a group of geometric elements of the same type, having the same physical properties.

This definition comprises:

• the concept of the regrouping of the geometric entities
• the concept of the definition of the physical properties

These two concepts are presented in the following sections.

## Geometric context

In the context of geometry building, we can distinguish four types of regions, corresponding to the four types of geometric entities: points, lines, faces, volumes.

These four types of regions are presented in the table below.

A region … regroups a group of …
volume volumes
surface faces
line lines
point points
having the same physical properties

## Physical context

In the physical approach, we can distinguish two types of regions: material regions and non-material regions.

These two types of regions are presented in the table below.

A region … is used to …
material model a material region
non-material impose boundary conditions

## Examples

The material regions are used to model of the material media:

• magnets, magnetic circuits, etc.
• fine air-gaps, thin sheets, etc.

The non-material regions are used to impose boundary conditions:

• normal field crossing a face, etc.
• imposed potential on a line, etc.