Circulation means movement in a loop or cycle that keeps going around. Your blood circulates through your body constantly: your heart pumps it out through arteries, it travels to every part of you, and then returns through veins to start the journey again. This continuous loop delivers oxygen and nutrients everywhere they're needed.

The word also describes how things move through a system or spread among people. A library tracks the circulation of its books: how many times each one gets checked out and returned. Newspapers measure their circulation by counting how many copies reach readers each day. Money circulates through an economy as people earn it, spend it, and pass it along to others.

When air circulates in a room, it moves around rather than staying still and stuffy. You might open windows to improve air circulation on a hot day. In a similar way, rumors can circulate through a school, spreading from student to student.

The verb form is circulate. You might circulate through a crowded party, moving from group to group. Teachers might ask students to circulate a permission slip, passing it from desk to desk so everyone can sign it. The key idea is always the same: something moving in a pattern that brings it back around again and again.