A ford is a place in a watercourse (most commonly a stream or river) that is shallow enough to be crossed by wading, on horseback, or in a wheeled vehicle. The names of many towns and villages are derived from such places, e.g. Oxford (a ford where oxen crossed the river: see the Oxford coat of arms), or Stratford (a ford on a Roman road). In some parts of the United States, fords are known as low-water crossings, or low-water "bridges", particularly when they are on a public road.
A ford is, clearly, a much cheaper form of river-crossing than a bridge though normally only suitable today for very minor roads. Most modern fords are shallow enough to be crossed by cars and other wheeled or tracked vehicles (a process known, fittingly, as "fording"), but they may become impassable after heavy rain.
At localities where the water is shallow enough, but the material on the riverbed will not support heavy vehicles, fords are sometimes improved by the provision of a submerged concrete floor. In such cases a curb is often placed on the downstream side to prevent vehicles slipping off, as growth of algae will often make the slab very slippery.
The German word furt (as in Frankfurt) and the Dutch voorde, (as in Coevorden, Dievoort, or Amersfoort) are cognate and have the same meaning.