What part of a syringe is referred to as the plunger?

The plunger of a syringe is the component that is pushed down to inject the liquid or medication contained within the syringe. It fits snugly inside the barrel and, when moved, creates a vacuum that draws liquid into the syringe or forces it out through the tip. The bottom of the syringe, where the plunger typically sits, plays a critical role in the operation of the device, making it the correct answer.

The other options refer to different parts of the syringe: the long tip is where the needle is attached, the barrel is the main cylindrical portion that holds the liquid, and the cap is used to cover the needle for safety and sterility. Each of these components has its own function, but in the context of identifying the part that is specifically called the plunger, the bottom is the appropriate answer.