Syringes are precision medical devices for injecting, withdrawing, or measuring liquids, consisting of a barrel (graduated cylinder holding medication), plunger (rubber-tipped piston for expulsion), flange (finger grip), and hub/nozzle for needle attachment. Types include hypodermic (1-60mL for IM/IV/subQ general use), insulin (0.3-1mL U-100 scale for diabetes), tuberculin (1mL fine gradations for TB tests), safety (retractable needles prevent sticks), auto-disable (single-use lockout for vaccines), oral (no needle for meds), and prefilled (factory-loaded e.g., heparin). Luer lock (threaded secure) vs. slip (friction fit) tips; disposable plastic dominates for sterility.