Oil sands, tar sands or, more technically, bituminous sands, are a type of unconventional petroleum deposit. The oil sands are loose sand or partially consolidated sandstone containing naturally occurring mixtures of sand, clay, and water, saturated with a dense and extremely viscous form of petroleum technically referred to as bitumen (or colloquially tar due to its similar appearance, odour and colour). Natural bitumen deposits are reported in many countries, but in particular are found in extremely large quantities in Canada. Other large reserves are located in Kazakhstan and Russia. Total natural bitumen reserves are estimated at 249.67 billion barrels (39.694×10^⁹ m³) globally, of which 176.8 billion barrels (28.11×10^⁹ m³), or 70.8%, are in Canada.

Oil sands reserves have only recently been considered to be part of the world's oil reserves, as higher oil prices and new technology enable them to be profitably extracted and upgraded to usable products. They are often referred to as unconventional oil or crude bitumen, in order to distinguish the bitumen extracted from oil sands from the free-flowing hydrocarbon mixtures known as crude oil traditionally produced from oil wells.

An oil is any substance that is liquid at ambient temperatures and does not mix with water but may mix with other oils and organic solvents. This general definition includes vegetable oils, volatile essential oils, petrochemical oils, and synthetic oils.

First attested in English 1176, the word oil comes from Old French "oile", from Latin "oleum", which in turn comes from the Greek "ἔλαιον" (elaion), "olive oil, oil" and that from "ἐλαία" (elaia), "olive tree". The earliest attested form of the word is the Mycenaean Greek e-ra-wo, written in Linear B syllabic script.

Organic oils are produced in remarkable diversity by plants, animals, and other organisms through natural metabolic processes. Lipid is the scientific term for the fatty acids, steroids and similar chemicals often found in the oils produced by living things, while oil refers to an overall mixture of chemicals. Organic oils may also contain chemicals other than lipids, including proteins, waxes and alkaloids.

Lipids can be classified by the way that they are made by an organism, their chemical structure and their limited solubility in water compared to oils. They have a high carbon and hydrogen content and are considerably lacking in oxygen compared to other organic compounds and minerals; they tend to be relatively nonpolar molecules, but may include both polar and nonpolar regions as in the case of phospholipids and steroids.

Andrew Nikiforuk is a Canadian journalist who has won multiple National Magazine Awards. His work has appeared in Saturday Night, Maclean’s, Canadian Business, Report on Business, Chatelaine, Alberta Views, Equinox,, Alternatives Journal and Canadian Family, and in both national newspapers. In 1990 the Toronto Star newspaper awarded him an Atkinson Fellowship in Public Policy to study AIDS and the failure of public health policy. His books include Tar Sands, Pandemonium, Fourth Horseman, and Saboteurs: Wiebo Ludwig’s War Against Oil, which won the Governor General’s Award in 2002.

In 2010, he became the Tyee's first writer in residence.

Empire of the Beetle: How Human Folly and a Tiny Bug Are Killing North America's Great Forests, Greystone Books, August 2011, paperback, 240 pages, ISBN 978-1-55365-510-7

Tar Sands: Dirty Oil and the Future of a Continent, Greystone Books, April 2010, paperback, 208 pages, ISBN 978-1-55365-555-8

Pandemonium: Bird Flu, mad Cow Disease and Other Biological Plagues of the 21st Century, Viking Canada (AHC), Hardcover, 320 pages, 978-0-67004-519-8

A German Requiem, To Words of the Holy Scriptures, Op. 45 (German: Ein deutsches Requiem, nach Worten der heiligen Schrift) by Johannes Brahms, is a large-scale work for chorus, orchestra, and a soprano and a baritone soloist, composed between 1865 and 1868. It comprises seven movements, which together last 65 to 80 minutes, making this work Brahms's longest composition. A German Requiem is sacred but non-liturgical, and unlike a long tradition of the Latin Requiem, A German Requiem, as its title states, is a Requiem in the German language.

Brahms's mother died in February 1865, a loss that caused him much grief and may well have inspired Ein deutsches Requiem. Brahms's lingering feelings over Robert Schumann's death in July 1856 may also have been a motivation, though his reticence about such matters makes this uncertain.

His original conception was for a work of six movements; according to their eventual places in the final version, these were movements 1–4 and 6–7. By the end of April 1865, Brahms had completed the first, second, and fourth movements. The second movement used some previously abandoned musical material written in 1854, the year of Schumann's mental collapse and attempted suicide, and of Brahms's move to Düsseldorf to assist Clara Schumann and her young children.