[uncountable, countable] the movement of something (for example air, water, gas, etc.)

Is circulate a noun or verb?

verb (used without object), cir·cu·lat·ed, cir·cu·lat·ing. to move in a circle or circuit; move or pass through a circuit back to the starting point: Blood circulates throughout the body. to pass from place to place, from person to person, etc.: She circulated among her guests.

What kind of word is circulation?

The act of moving in a circle, or in a course which brings the moving body to the place where its motion began. The act of passing from place to place or person to person; free diffusion; transmission.