A trench is a type of excavation or depression in the ground. Trenches are generally defined by being deeper than they are wide (as opposed to a wider gully or ditch), and by being narrow compared to their length (as opposed to a simple hole).

Trench shoring is often used in trenchworks to protect workers and stabilize embankments.

Some trenches are created as a result of erosion by rivers (which may have long since fallen dry), others are created by geological movement of tectonic plates, such as rift valleys or more commonly oceanic trenches. Some oceanic trenches include the Mariana Trench and the Challenger Deep. The latter form is relatively deep (ca. 10 km), linear and narrow, and is formed by plate subduction when plates converge.

In the civil engineering field of construction or maintenance of infrastructure, trenches play a major role. They may be created to search for pipes and other infrastructure that is known to be underground in the general area, but whose exact location has been lost ('search trench' or 'search slit'). They are also used to underground easily damaged and obstructive infrastructure or utilities (such as gas mains, water mains or telephone lines). A similar use for higher bulk would be in pipeline transport. Finally, trenches may be created as the first step of creating a foundation wall.

Daniel Robert Snow (born 3 December 1978) is an English television presenter. He has presented and appeared in many popular history-related programmes for the BBC and is the "History Hunter" for The One Show.

Dan Snow is the youngest son of Peter Snow, BBC television journalist, and Ann MacMillan, Managing Editor of CBC London Bureau. Dan therefore has joint British/Canadian citizenship. Through his mother, he is the nephew of Canadian historian Margaret MacMillan, and a great-great-grandson of British Prime Minister David Lloyd George. One of his father's cousins is the Channel 4 news reporter Jon Snow.

Snow was educated at Barnes Primary School and St Paul's School, an independent school in Barnes in south London, where he was Captain of the School, followed by Balliol College at Oxford. He rowed three times in the University Boat Race, winning in 2000 and losing a controversial race, when president, in 2001. He received a double first-class honours degree in Modern History.

In 2003, Snow and his father made a programme on El Alamein to commemorate the 60th anniversary of the battles and followed this up with an eight-part series on BBC2 in 2004 called Battlefield Britain. This won a BAFTA award for special effects. The same year Snow won a Sony award as one of the presenters on LBC Boat Race coverage.