primary business; main function; core focus
Refers to the central activity, role, or responsibility of an organization, department, or role. Often used in business or administrative contexts.
Our company's primary business is software development.
Please clarify the primary functions of this department.
本業 refers to one's main occupation or core business, often contrasted with side jobs. 主要業務 is more about the primary tasks or functions within a given role or organization.
主業務 is a near-synonym but less common; 主要業務 is the more standard compound for 'primary business/function'.
Compound of 主要 (primary, main) and 業務 (business, operations).