Phlebitis is defined as:

Phlebitis is specifically defined as inflammation of a vein. This condition can occur in association with thrombosis (blood clot formation) or can be caused by irritation from intravenous (IV) catheters, among other factors. The inflammation in the vein can lead to pain, swelling, and redness in the affected area, which can be quite challenging for patients if left untreated. Proper identification and management of phlebitis are essential, especially for individuals who may have undergone procedures involving venous access. Understanding this condition is vital for those working in healthcare, as timely intervention can prevent complications such as deep vein thrombosis.

The other options refer to different types of inflammation that do not align with the specific definition of phlebitis: inflammation of arteries, the heart, or nervous tissue each pertains to distinct medical conditions and anatomical considerations separate from venous inflammation.