Oyster card

The Oyster card is a form of electronic ticketing used on public transport in Greater London in the United Kingdom. It is promoted by Transport for London and is valid on travel modes across London including London Underground, London Buses, the Docklands Light Railway (DLR), London Overground, trams, some river boat services, and most National Rail services within the London fare zones.

A standard Oyster card is a blue credit-card-sized stored-value contactless smartcard that can hold single tickets, period tickets and travel permits, which must be added to the card before travel. Passengers touch it on an electronic reader when entering and leaving the transport system in order to validate it or deduct funds. Cards may be "topped-up" by recurring payment authority, by online purchase, at credit card terminals or by cash, the last two methods at stations or ticket offices. The card is designed to reduce the number of transactions at ticket offices and the number of paper tickets. Usage is encouraged by offering substantially cheaper fares than with cash though the acceptance of cash is being phased out. On London buses, cash is no longer accepted.

Oyster

The word oyster is used as a common name for a number of different families of saltwater clams, bivalve molluscs that live in marine or brackish habitats. In some species the valves are highly calcified, and many are somewhat irregular in shape. Many, but not all, oysters are in the superfamily Ostreoidea.

Some kinds of oysters are commonly consumed by humans, cooked or raw, the latter being a delicacy. Some kinds of pearl oysters are harvested for the pearl produced within the mantle. Windowpane oysters are harvested for their translucent shells, which are used to make various kinds of decorative objects.

Etymology

First attested in English during the 14th century, the word "oyster" comes from Old French oistre, in turn from Latin ostrea, the feminine form of ostreum, which is the latinisation of the Greek ὄστρεον (ostreon), "oyster". Compare ὀστέον (osteon), "bone".

Types

True oysters

True oysters are members of the family Ostreidae. This family includes the edible oysters, which mainly belong to the genera Ostrea, Crassostrea, Ostreola, and Saccostrea. Examples include the Belon oyster, eastern oyster, Olympia oyster, Pacific oyster, and the Sydney rock oyster.

London

London ⁱ/ˈlʌndən/ is the capital and most populous city of England and the United Kingdom. Standing on the River Thames, London has been a major settlement for two millennia. It was founded by the Romans, who named it Londinium. London's ancient core, the City of London, largely retains its 1.12-square-mile (2.9 km²) medieval boundaries and in 2011 had a resident population of 7,375, making it the smallest city in England. Since at least the 19th century, the term London has also referred to the metropolis developed around this core. The bulk of this conurbation forms Greater London, a region of England governed by the Mayor of London and the London Assembly. The conurbation also covers two English counties: the small district of the City of London and the county of Greater London. The latter constitutes the vast majority of London, though historically it was split between Middlesex (a now abolished county), Essex, Surrey, Kent and Hertfordshire.