The Doppler effect (or Doppler shift), named after the Austrian physicist Christian Doppler, who proposed it in 1842 in Prague, is the change in frequency of a wave (or other periodic event) for an observer moving relative to its source. It is commonly heard when a vehicle sounding a siren or horn approaches, passes, and recedes from an observer. The received frequency is higher (compared to the emitted frequency) during the approach, it is identical at the instant of passing by, and it is lower during the recession.

The South Shore Estuary is an estuary located along the south shore of Long Island, between the mainland and the outer barrier islands, in eastern New York state. It stretches for over 70 miles (110 km) from West Bay in Nassau County to the Shinnecock Bay in Suffolk County.

Deadweight tonnage is a measure of how much weight a ship is carrying or can safely carry. It is the sum of the weights of cargo, fuel, fresh water, ballast water, provisions, passengers, and crew.

Conan of Aquilonia is a collection of four linked fantasy short stories written by L. Sprague de Camp and Lin Carter featuring Robert E. Howard's seminal sword and sorcery hero Conan the Barbarian. The stories were originally published in Fantastic for August 1972, July 1973, July 1974, and February, 1975. The collected stories were intended for book publication by Lancer Books, but this edition never appeared due to Lancer's bankruptcy. The first book edition was issued in paperback by Ace Books in May 1977 and the first British edition was published by Sphere Books in October 1978.

A perennial stream or perennial river is a stream or river (channel) that has continuous flow in parts of its stream bed all year round during years of normal rainfall. "Perennial" streams are contrasted with "intermittent" streams which normally cease flowing for weeks or months each year, and with "ephemeral" channels that flow only for hours or days following rainfall.