Celtic
A rather misused term, which really ought to be reserved for references to languages. In fact, it is used for art styles and racial or ethnic types and even as a geographical and chronological term. Best avoided if you can think of a more specific or accurate word!

Charters
These were used particularly for the land grants and transactions of the Anglo-Saxon period, whereby the king granted blocks of land to monasteries and individuals. Such charters often record the boundaries of the land, making them some of the finest records for placenames and details of the Anglo-Saxon countryside.

Christians
There were certainly Christians in Britain in the latter part of the Roman period, before 400 AD, and there were monasteries in Ireland and probably in western Britain as well by the later 5th and 6th centuries. The Saxons then introduced their own form of paganism. England began to be converted to Christianity following the missions of Northumbrian monks, via Iona and Lindisfarne, and the mission of Augustine to Kent beginning in 597 AD. Over the next century, the country was converted by his followers and by monks from the Northumbrian Church, resulting finally in the conversion of the Isle of Wight in 686 AD. Theodore of Tarsus, Archbishop of Canterbury, carried out a thorough reorganisation of the Church between 669 and 690 AD.

Coins
To an archaeologist, coins are invaluable as prime dating material. When they were produced (ie minted) is usually known; indeed, many of them were issued to commemorate certain events or were in some other way dated. Obviously a coin found on a site can only date from the earliest time that that coin became available. If it is in mint condition, the layer or context with which it is associated may be of the same date as the coin, whereas if the coin is well worn, it may well have been deposited (lost or buried) some time after it was produced. Thus, all the other things found with or around the coin can be roughly dated. A great deal of archaeology in the past has been based on this relatively simple idea. See also terminus post quem/terminus ante quem.

Computer graphics
A catch-all term for all the computer techniques now available to help archaeologists in many aspects of their work. Uses of the computer range from accurate plans with data gathered from many sources and all depicted on the same base map, to elaborate programs that enable the three-dimensional reconstruction of sites on screen so that we can 'travel' through them, viewing the sites from different angles. Time Team use a number of these techniques, including those associated with mapping, geophysics survey and reconstruction drawings. For details of some of the computer programmes used by Time Team see the FAQs.

Conchoidal rings
Flints occur commonly on early sites and, during fieldwork, conchoidal rings can be found almost everywhere. The problem is to know whether they were made by prehistoric people or are the result of the natural weathering of blocks of flint by frost and so on. One way is to look for the characteristic marks produced when flint blades were detached from a core by flintworkers. A blade produced by a blow to the top of a block of flint will have a 'point of percussion', a 'bulb of percussion' below, and below that a series of 'ripples' or 'conchoidal rings', evidence of how the force of the blow has passed through the flint. Although the blade may then have had other flakes removed to make it into a tool, these characteristic features are a good guide to whether a particular flint was man-made.

Context
A vague word used by archaeologists to describe the position of a particular find or site in relation to other things. In fact, the context of a find or feature is of prime importance since it is only when its relationship to others is understood that some progress can be made in the investigation of a site. This is why objects removed by looting, whether after treasure hunting or other raiding, are of less value to archaeologists, in terms of the information they can give, than those carefully recorded as they are excavated. Out of the context in which they existed in the ground along with all the other earlier, later and contemporary features, objects and deposits, they can only be appreciated as single unrelated items.

Cropmarks
See aerial photography. These are light and dark marks visible in growing and ripening crops, which reflect the differences in the subsoil beneath. Thus parched lines of grass may indicate hidden stone walls or packed stone layers such as Roman roads, and much greener grass may be growing over pits, ditches or gulleys. As crops, particularly cereals, come to maturity, any parts that are short of water will tend to grow less and to ripen first, while areas of crops over pits and ditches will tend to remain greener that bit longer, and be taller than the rest. Very large numbers of new cropmark sites have been found since the 1960s, and there are probably still very many more to be found.

In practice, however, it is often difficult to see why some cropmarks form at all. In many cases, their appearance is related to the geology, the weather at the time the crop was sown and/or is growing, and numerous other factors. Many are also formed as a result of modern activities: leaky muck spreaders, erratic sprinklers and tethered goats have all produced spectacularly 'archaeological' cropmarks!

Cruck
A term employed in the study of buildings to describe timbers used in roof supports. Crucks or cruck blades are inclined posts often split in two to give matching pairs to support the roof ridge from which the rest of the roof hangs. The side walls can then be fitted in beneath without the roof weighing on them. Pairs of crucks are arranged down the building at intervals (in bays); large barns can have many pairs. The technique is often said to be Saxon, but cruck buildings were built right down to recent times.