Ambulance - ambulant
Don't confuse the two words ambulance and ambulant, which is most commonly an adjective, but can be used substantively, and then has the plural ambulants. Both sound the same, except in the most careful speech. They are derived from the Latin root ambulāre, a verb meaning 'to walk'. (This also gives the old-fashioned perambulator, now usually pram, and 'to amble'. Somnambulant, or somnambulist (Latin somnum 'sleep'), is a formal word for a sleep-walker, as is the slightly less precise noctambulant (Latin nocte 'by night') for one who walks at night. A funambulist is archaic English for modern 'tight-rope walker' - its equivalent is currently the regular word in French, and other Romance languages.)
- An ambulance is an emergency vehicle for carrying the sick, wounded or injured. The original ambulances were used in the Crimean War as "moving hospitals" (OED); what we now call 'an ambulance' was then 'an ambulance wagon', using the word ambulance epithetically. The British learned to care for their military wounded from their Crimean allies, the French, who had begun their development under Napoleon.
- There are increasingly 'non-emergency ambulances', used, for example, for carrying those who cannot make their own way to and from various clinics; but the basic idea is that of the emergency vehicle that sounds its sirens in city streets, leading many children to know it as 'an ooo-aaa'.
- Ambulant is simply an adjective meaning 'walking'. It is often used to distinguish between those patients who can reach care by their own efforts, for example after a train crash, while - paradoxically - the non-ambulants have to wait for the ambulance to transport them to hospital. The ambulants can travel in less specialized vehicles to which they can walk.