What is a Subdomain?

When working on a project guided by Domain Driven Design, there are always multiple parts that are involved in a domain. Trying to understand a domain as a whole is not the best approach in these types of projects. It is necessary to break the domain into smaller pieces called subdomains to better understand the domain that is being modeled.

What exactly is a subdomain?

A subdomain is nothing but a sub-process of the domain. In other words, a domain is made up of several different activities. These activities are called subdomains. The image below shows how a domain has different sub-parts where every sub-part is a subdomain.