Suction is the force that pulls or holds things together when air pressure pushes from one direction more than another. When you sip through a straw, you're not actually sucking the liquid up. Instead, you're removing air from inside the straw, and the normal air pressure outside pushes the drink up into your mouth. That pushing force is what we call suction.

You can see suction at work when you press a rubber suction cup against a smooth surface like a window or tile. Pushing out the air from under the cup creates lower pressure there, so the higher air pressure outside holds it tight against the surface. The bigger the difference in pressure, the stronger the suction.

Vacuum cleaners use suction to pull dirt and dust into their bags. Octopuses use suction cups on their arms to grip prey and climb across rocks. Doctors sometimes use suction to remove fluids during medical procedures.

The word can also describe the sound of something being pulled by suction, like the squelching suction of boots being pulled from thick mud. When something has suction power, it means it can create that pulling force effectively.