Christopher Chippendale's Stonehenge Complete gives the derivation of Stonehenge as coming from the Old English words "stān" meaning "stone", and either "hencg" meaning "hinge" (because the stone lintels hinge on the upright stones) or "hen(c)en" meaning "gallows" or "instrument of torture". Medieval gallows consisted of two uprights with a lintel joining them, resembling Stonehenge's trilithons, rather than looking like the inverted L-shape more familiar today.

The "henge" portion has given its name to a class of monuments known as henges. Archaeologists define henges as earthworks consisting of a circular banked enclosure with an internal ditch. As often happens in archaeological terminology, this is a holdover from antiquarian usage, and Stonehenge cannot in fact be truly classified as a henge site as its bank is inside its ditch. Despite being contemporary with true Neolithic henges and stone circles, Stonehenge is in many ways atypical. For example, its extant trilithons make it unique. Stonehenge is only distantly related to the other stones circles in the British Isles, such as the Ring of Brodgar.

The first monument consisted of a circular bank and ditch enclosure (7 and 8) measuring around 110 m (360 feet) in diameter with a large entrance to the north east and a smaller one to the south (14). It stood in open grassland on a slightly sloping but not especially remarkable spot. The builders placed the bones of deer and oxen in the bottom of the ditch as well as some worked flint tools. The bones were considerably older than the antler picks used to dig the ditch and the people who buried them had looked after them for some time prior to burial. The ditch itself was continuous but had been dug in sections, like the ditches of the earlier causewayed enclosures in the area. The chalk dug from the ditch was piled up to form the bank. This first stage is dated to around 3100 BC after which the ditch began to silt up naturally and was not cleared out by the builders. Within the outer edge of the enclosed area was dug a circle of 56 pits, each around 1m in diameter (13), known as the Aubrey holes after John Aubrey, the seventeenth century antiquarian who was thought to have first identified them. The pits may have contained standing timbers, creating a timber circle although there is no excavated evidence of them. A small outer bank beyond the ditch could also date to this period (9)..

Many early historians were influenced by supernatural folktales in their explanations. Some legends held that Merlin the wizard had a giant build the structure for him or that he had magically transported it from Mount Killaraus in Ireland, while others held the Devil responsible. Henry of Huntingdon was the first to write of the monument around 1130 soon followed by Geoffrey of Monmouth who was the first to record fanciful associations with King Arthur which led the monument to be incorporated into the wider cycle of European medieval romance.

In 1615, Inigo Jones argued that Stonehenge was a Roman temple, dedicated to Caelus, (a Latin name for the Greek sky-god Ouranos), and built following the Tuscan order. Later commentators maintained that the Danes erected it. Indeed, up until the late nineteenth century, the site was commonly attributed to the Saxons or other relatively recent societies.

The first academic effort to survey and understand the monument was made around 1640 by John Aubrey. He declared Stonehenge the work of Druids. This view was greatly popularised by William Stukeley. Aubrey also contributed the first measured drawings of the site, which permitted greater analysis of its form and significance. From this work, he was able to demonstrate an astronomical or calendrical role in the stones' placement.

By the turn of the nineteenth century, John Lubbock was able to attribute the site to the Bronze Age based on the bronze objects found in the nearby barrows.

The early attempts to figure out the people who had undertaken this colossal project have since been debunked. While there have been precious few in the way of real theories to explain who built the site, or why, there can be an assessment of what we know to be fact and what has been proven false.

First there is the matter of radio carbon dating the construction of the site itself. As has been already stated in the construction outlines above, the monument building of the site began around the year 3100 BC and ended around the year 1600. This allows the elimination of a few of the theories that have been presented. The original theory that the Druids were the ones who built the site can be discounted first since it is the more popular one. The Celtic society that spawned the Druid priesthood came into being only after the year 300 BC. In addition to this, the theory that the Druids using the site for sacrifices is thin, considering that the Druids were pagans and performed the majority of their rituals in the woods or mountains, areas better suited for “earth rituals” than an open field.
As to the other theory relating to the Romans, this is more ludicrous yet. The Romans never even came to the British Isles until they conquered the land in 43AD. The theories of Inigo Jones and others that Stonehenge was built as a Roman temple have been long dismissed. They were early theories, and when the actual dates of construction came out, any talk of merely early Saxon or Roman workers building the site are no longer considered. Other popular notions mentioned, aliens coming to Earth to build primitive man a map to the stars were dismissed out of hand, since besides being utterly impractical (why would aliens give a species that could barely write such a gift?), There is absolutely no physical evidence to back it up, save unsupported supposition about the frequency of these sites in the area. The problem with this is that who we do not know who originally started building it or the purpose behind it. It is difficult to imagine it being built for uses only one or two days in the year. And since it appears that it was built in three or four distinct stages, it is virtually impossible to tell what the purpose might have been since it was obviously worked on by a number of different cultures.

Other theories that have been taken out of consideration were the idea that Egyptian or Mycenaean or even Greek cultures, which coincided with the popular belief that these cultures infused Europe with Bronze Age culture. After the testing showed that the megalithic structures in both England and France predate these cultures, they were removed. Also mentioned on this site are the findings of John Lubbock at the turn of the 19th century that point to this site being a Bronze Age creation, based on axe heads and daggers and other artifacts that have been found. However, a number of carvings that were also thought to point to Bronze Age origin have since been refuted as being put in later, raising the serious question of whether or not the artifacts were used in the site or buried there at a later date in some sort of funerary rites.

The question that dominates the debate as to what Stonehenge was used for can be easily divided into those that believe it to be a religious or a scientific observatory. The scientific idea carries more weight. As outlined in the theories section below, Gerald Hawkins noted 165 key sites that he stated correlated very strongly with the rising and setting points of the sun and moon. He believed that because of this, the site could be used to anticipate interstellar phenomena. There have been odd occurrences, like the Hale-Bopp comet passing directly over this site at the turnoff the millennia to support this theory. This has sparked that the idea that the site was created in order to help commemorate the solstices, as the alignment with the sun and moon would seem to indicate.

Further supporting this line of evidence is the fact that the site’s alignment is focused along the lunar lines in a way that increases the accuracy of procession, which is the amount that the Earth’s slight tilt on its axis, or “wobble” Will eventually change the timing of lunar events. In short, this site could have been set up to more accurately predict events taking place in the heavens above. While there is still no conclusive evidence that this site was indeed intended for use as an observatory, the fact also that

Much of the support for the religious use for this has come from a purely political standpoint. The modern Celts, who were for a long time believed to be the creators of the site, have moved quickly to claim the site as their own. They now hold festivals and ceremonies at different times during the year. The problem with this has been outlined above, with the carbon dating refuting their hand in the site’s creation. There are a number of assumptions that have supported this theory, however. It is known that on the longest day of the year, the summer solstice, the sun shines directly through the center of the structure, which given many of the cultural attitudes of sun worship that were rampant at the time, seems to indicate a religious purpose. In addition, much of what survives from the distant past, buildings, etc., have all been religious in nature.

Again, much of the early interpretations as to the nature of this site and the reason for its construction can be theorized and speculated upon, but there is no bulk of hard evidence to point us in one direction or the other. There are portions of the site that have not been excavated, such as the West portion, so there remain possible hard facts out there. All we can say for certain at this point is when it was built and the mathematical facts stated above that go along with it.

Many archaeologists believe Stonehenge was an attempt to render in permanent stone the more common timber structures that dotted Salisbury Plain at the time, such as those that stood at Durrington Walls. Modern anthropological evidence has been used by Mike Parker Pearson and the Malagasy archaeologist Ramilisonina to suggest that timber was associated with the living and stone with the ancestral dead amongst prehistoric peoples. They have argued that Stonehenge was the terminus of a long, ritualised funerary procession for treating the dead, which began in the east, during sunrise at Woodhenge and Durrington Walls, moved down the Avon and then along the Avenue reaching Stonehenge in the west at sunset. The journey from wood to stone via water was, they consider, a symbolic journey from life to death. There is no satisfactory evidence to suggest that Stonehenge's astronomical alignments were anything more than symbolic and current interpretations favour a ritual role for the monument that takes into account its numerous burials and its presence within a wider landscape of sacred sites. Many also believe that the site may have had astrological/spiritual significance attached to it.

Much speculation has surrounded the engineering feats required to build Stonehenge. Assuming the bluestones were brought from Wales by hand, and not transported by glaciers as Aubrey Burl has claimed, various methods of moving them relying only on timber and rope have been suggested. In a 2001 exercise in experimental archaeology, an attempt was made to transport a large stone along a land and sea route from Wales to Stonehenge. Volunteers pulled it for some miles (with great difficulty) on a wooden sledge over land, using modern roads and low-friction netting to assist sliding, but once transferred to a replica prehistoric boat, the stone sank in Milford Haven, before it even reached the rough seas of the Bristol Channel.

As far as positioning the stones, it has been suggested that timber A-frames were erected to raise the stones, and that teams of people then hauled them upright using ropes. The topmost stones may have been raised up incrementally on timber platforms and slid into place or pushed up ramps. The carpentry-type joints used on the stones imply a people well skilled in woodworking and they could easily have had the knowledge to erect the monument using such methods. In 2003 retired construction worker Wally Wallington demonstrated ingenious techniques based on fundamental principles of levers, fulcrums and counterweights to show that a single man can rotate, walk, lift and tip a ten-ton cast-concrete monolith into an upright position. He is progressing with his plan to construct a simulated Stonehenge comprising of eight uprights and two lintels.

Alexander Thom was of the opinion that the site was laid out with the necessary precision using his megalithic yard.

The engraved weapons on the sarsens are unique in megalithic art in the British Isles, where more abstract designs were invariably favoured. Similarly, the horseshoe arrangements of stones are unusual in a culture that otherwise arranged stones in circles. The axe motif is, however, common to the peoples of Brittany at the time, and it has been suggested at least two stages of Stonehenge were built under continental influence. This would go some way towards explaining the monument's atypical design, but overall, Stonehenge is still inexplicably unusual in the context of any prehistoric European culture.

Estimates of the manpower needed to build Stonehenge put the total effort involved at millions of hours of work. Stonehenge 1 probably needed around 11,000 man-hours (or 460 man-days) of work, Stonehenge 2 around 360,000 (15,000 man-days or 41 years) and the various parts of Stonehenge 3 may have involved up to 1.75 million hours (73 000 days or 200 years) of work. The working of the stones is estimated to have required around 20 million hours (830 000 days or 2300 years) of work using the primitive tools available at the time. Certainly, the will to produce such a site must have been strong, and it is considered that advanced social organisation would have been necessary to build and maintain it.

By the beginning of the 20th century a number of the stones had fallen or were leaning precariously, probably due to the increase in curious visitors clambering on them during the nineteenth century. Three phases of conservation work were undertaken which righted some unstable or fallen stones and carefully replaced them in their original positions using information from antiquarian drawings.

Stonehenge is a place of pilgrimage for neo-druids and those following pagan or neo-pagan beliefs. The midsummer sunrise began attracting modern visitors in 1870s, with the first record of recreated Druidic practices dating to 1905 when the Ancient Order of Druids enacted a ceremony. Despite efforts by archaeologists and historians to stress the differences between the Iron Age Druidic religion, the much older monument and modern Druidry, Stonehenge has become increasingly, almost inextricably, associated with British Druidism, Neo Paganism and New Age philosophy.

The earlier rituals were augmented by the Stonehenge free festival, held between 1972 and 1984, and loosely organised by the Politantric Circle. However, in 1985 the site was closed to festivalgoers by English Heritage and the National Trust by which time the number of midsummer visitors had risen from 500 to 30,000. A consequence of the end of the festival was the violent confrontation between the police and new age travellers that became known as the Battle of the Beanfield when police blockaded a convoy of travellers to prevent them from approaching Stonehenge. There was then no midsummer access for almost fifteen years until limited opening was negotiated in 2000.

In more recent years, the setting of the monument has been affected by the proximity of the A303 road between Amesbury and Winterbourne Stoke, and the A344. In early 2003, the Department for Transport announced that the A303 would be upgraded, including the construction of the Stonehenge road tunnel. The controversial plans have not yet been finalised by the government.

Also announced has been a new heritage centre, which was intended to be open in 2006. Current provision for visitors has often been criticised; in 1993 Stonehenge's presentation was condemned by the Public Accounts Committee of the British House of Commons as 'a national disgrace'. English Heritage proposes a new purpose-built facility 3km from the stones at Countess Road in Amesbury, on the edge of the World Heritage Site boundary. Locals in Amesbury have complained that the scheme would shift traffic congestion from Stonehenge to their own village. They have also suggested that the necessary time that the public would now have to spend travelling to and from Stonehenge would likely dissuade many visitors, especially American and Japanese tourists on whistle-stop tours of England, from visiting at all.

In July 2005 the plans were thrown into uncertainty following refusal of planning permission for the visitors' centre by Salisbury District Council whilst the British government placed the rising costs of the road scheme under review.

There is a full-size replica of Stonehenge as it would have been before decay at Maryhill in Washington state, built by Sam Hill as a war memorial. Stonehenge Aotearoa in the Wairarapa region of New Zealand is a modern adaptation aligned with the astronomy seen from the Antipodes; it was built by the Phoenix Astronomical Society from wood and sprayed concrete. The University of Missouri at Rolla has a half-scale replica located on campus, UMR Stonehenge. East Stroudsburg University, in East Stroudsburg, Pennsylvania, has a small replica on its campus dubbed "Stroudhenge".

Carhenge was constructed from vintage American cars near Alliance, Nebraska by the artist Jim Reynolds in 1987. Another replica, called Stonehenge II, in Texas is constructed from an adobe-like material. Tankhenge existed in the border zone of Berlin in the early 1990s after the collapse of the Wall. Tankhenge was constructed from three ex-Soviet armoured personnel carriers.

A full-size Stonehenge made out of foam — and inevitably called Foamhenge — stands near Natural Bridge, Virginia *.

Another modern take on Stonehenge exists outside of Sante Fe, New Mexico, constructed out of junked refrigerators, known as 'Fridgehenge'. The site was created by the artist Adam Jonas Horowitz. *

Another full-size exact replica of what Stonehenge would have looked like 4000 years ago, also made of foam, was constructed and erected just 10 mi southwest of the actual Stonehenge. It was used for scientific and archaeological studies and was removed after.

The rock band Black Sabbath featured a Stonehenge stage set for the 1983-1984 Born Again tour that ended up being too large to fit in most venues. This was parodied in the movie This is Spinal Tap, when the band orders a Stonehenge set but it arrives in miniature due to a confusion between feet and inches. There was also a Chicago based heavy metal band named Stonehenge that actually owned the trademark to the name. Stonehenge met with underground success in the 1990's - 2000's performing with acts such as Pantera, Iced Earth, Trouble and Manowar.

In the MMORPG Runescape, there is a Stonehenge look-alike sometimes refered to as "Runehenge (rune being taken from the name of the game)

Aside from modern replicas, several other archaeological sites have had Stonehenge's name partially or fully incorporated into their own names. America's Stonehenge is an unusual and controversial site in New Hampshire. A henge near Stonehenge containing concentric rings of postholes for standing timbers, discovered in 1922, was named Woodhenge by its excavators because of similarities with Stonehenge. The timber Seahenge in Norfolk was named as such by journalists writing about its discovery in 1998.

In May 2006, reports emerged of an "Amazon Stonehenge" Calcoene, 390 kilometres from Macapa, the capital of Amapa state, near Brazil's border with French Guyana. It is comprised of 127 stones, possibly forming astronomical observing points.