Trocar is a surgical instrument used to puncture body cavities. Its synonyms include cannula, puncture needle, and hollow needle. A cannula is a tube inserted into a body cavity to drain fluids or inject medicine. A puncture needle is a sharp object used for piercing a surface, while a hollow needle is a needle with a hollow center used for withdrawing fluids or injecting substances. Trocars, cannulas, puncture needles, and hollow needles are medical instruments used for minimally invasive procedures. Their purpose is to provide access to body cavities without making large incisions, which can cause more pain and longer recovery times.