In software engineering, domain is the targeted subject area of a computer program.
Formally it represents the target subject of a specific programming project, whether narrowly or broadly defined.
[1] Domain in the realm of software engineering commonly refers to the subject area on which the application is intended to apply.
—Andrew Powell-Morse[2] Domain: A sphere of knowledge, influence, or activity.
The subject area to which the user applies a program is the domain of the software.