A megalith is a large stone that has been used to construct a structure or monument, either alone or together with other stones. The word "megalithic" describes structures made of such large stones, utilizing an interlocking system without the use of mortar or cement, as well as representing periods of prehistory characterised by such constructions. For later periods the term monolith, with an overlapping meaning, is more likely to be used.
The word "megalith" comes from the Ancient Greek "μέγας" (megas) meaning "great" and "λίθος" (lithos) meaning "stone." Megalith also denotes an item consisting of rock(s) hewn in definite shapes for special purposes. It has been used to describe buildings built by people from many parts of the world living in many different periods. A variety of large stones are seen as megaliths, with the most widely known megaliths not being sepulchral. The construction of these structures took place mainly in the Neolithic (though earlier Mesolithic examples are known) and continued into the Chalcolithic and Bronze Age.
A menhir (French, from Middle Breton : men, stone + hir, long), standing stone, orthostat, or lith is a large upright standing stone. Menhirs may be found singly as monoliths, or as part of a group of similar stones. Their size can vary considerably, but their shape is generally uneven and squared, often tapering towards the top. Menhirs are widely distributed across Europe, Africa and Asia, but are most numerous in Western Europe; in particular in Ireland, Great Britain and Brittany. There are about 50,000 megaliths in these areas, while there are 1,200 menhirs in northwest France alone. Standing stones are usually difficult to date, but pottery found underneath some in Atlantic Europe connects them with the Beaker people. They were constructed during many different periods across pre-history, and they were erected as part of a larger megalithic culture that flourished in Europe and beyond.
Some menhirs have been raised next to buildings which often have some early or current religious significance. One example is the South Zeal Menhir in Devon, which formed the basis for a 12th-century monastery built by lay monks. The monastery later became the Oxenham Arms Hotel at South Zeal, and the standing stone remains in place in the ancient snug bar at the hotel.
Where they appear in groups, often in a circular, oval, henge or horseshoe formation, they are sometimes called megalithic monuments. These are sites of ancient religious ceremonies, sometimes containing burial chambers. The exact function of menhirs has provoked more debate than practically any other issue in European pre-history. Over the centuries, they have variously been thought to have been used by Druids for human sacrifice, used as territorial markers or elements of a complex ideological system, or functioned as early calendars. Until the nineteenth century, antiquarians did not have substantial knowledge of prehistory; and their only reference points were provided by Classical literature. The developments of radiocarbon dating and tree-ring calibration have done much to further human knowledge in this area.