The term ambulance comes from the Latin word ambulare, meaning to walk or move about which is a reference to early medical care where patients were moved by lifting or wheeling. The word originally meant a moving hospital which follows an army in its movements. During the American Civil War vehicles for conveying the wounded off the field of battle were called ambulance wagons. Field hospitals were still called ambulances during the Franco-Prussian War of 1870 and in the Serbo-Turkish war of 1876 even though the wagons were first referred to as ambulances about 1854 during the Crimean War.

Nowadays the word is most commonly associated with the land-based, emergency motor vehicles that administer emergency care to those with acute illnesses or injuries, hereafter known as emergency ambulances. These are usually fitted with flashing warning lights and sirens to facilitate their movement through traffic. It is these emergency ambulances that are most likely to display the Star of Life, which represents the six stages of prehospital medical care.

There are other types of ambulance, with the most common being the patient transport ambulance. These vehicles are not usually (although there are exceptions) equipped with life-support equipment, and are usually crewed by staff with fewer qualifications than the crew of emergency ambulances. Their purpose is simply to transport patients to, from or between places of treatment. In most countries, these are not equipped with flashing lights or sirens.

Other vehicles used as ambulances include trucks, vans, station wagons, buses, helicopters, fixed-wing aircraft, boats, and even hospital ships.

Functional types

Ambulances can be grouped into types depending on whether or not they transport patients, and under what conditions. In some cases, ambulances may fulfil more than one function (such as combining emergency ambulance care with patient transport).