A neck order is a type of decoration which is designed to be worn and displayed around a person's neck, rather than hung (draped) from the chest as is the standard practice for displaying most decorations.
Most of the insignia of orders are issued in several degrees which typically include a neck order version for Commanders and Grand Officers. In countries which do not typically bestow orders with degrees, neck orders are still usually considered to be high-ranking decorations.
In the Middle Ages most orders were worn on a collar – see livery collar. Later, in the 17th century the insignia were worn hanging from a ribbon around the neck. When, in the late 18th century, orders were divided into several classes, the cross on a ribbon around the neck became the privilege of a commander. A decoration in that rank is usually awarded to high-ranking officials like brigadiers, consuls and secretaries of State.
A female usually wears her commander's cross on a bow on the shoulder of her dress.
In the 19th century it was not unusual to wear a Grand Cross, normally hanging from a ribbon over the shoulder to the hip as a neck order when this was considered more convenient or when another Grand Cross was worn.
^USAMilitaryMedals.com: Legion of Merit Medal Ribbon; n.b., The Legion of Merit is one of only two United States military decorations to be issued as a neck order (the other being the Medal of Honor), and the only United States decoration which may be issued in award degrees (much like an Order of chivalry or certain Orders of Merit).