The executive branch
bureau
A subdivision inside a department with its own mission and, usually, its own statute: the FBI inside Justice, the Census Bureau inside Commerce.
In full
Bureau, administration, service, and office are used loosely for the same kind of unit. What matters is not the label but where the unit's authority comes from: a bureau acting under its own statute has an independent legal footing, while one acting purely on the department's delegation does not. Names change with reorganizations; statutory authority usually does not.
Where to go next
Keep going
Browse every term in the glossary, or see the vocabulary in motion in the How government works walkthroughs.
A plain-language explanation for civic education, not legal advice. When in doubt, the official source named above controls.