A central branch of metaphysics is ontology, the investigation into what types of things there are in the world and what relations these things bear to one another. The metaphysician also attempts to clarify the notions by which people understand the world, including existence, objecthood, property, space, time, causality, and possibility.

Like all proteins, enzymes are made as long, linear chains of amino acids that fold to produce a three-dimensional product. Each unique amino acid sequence produces a specific structure, which has unique properties. Individual protein chains may sometimes group together to form a protein complex. Most enzymes can be denatured—that is, unfolded and inactivated—by heating or chemical denaturants, which disrupt the three-dimensional structure of the protein. Depending on the enzyme, denaturation may be reversible or irreversible.

A car rental or car hire agency is a company that rents automobiles for short periods of time (generally ranging from a few hours to a few weeks) for a fee. It is an elaborate form of a rental shop, often organized with numerous local branches (which allow a user to return a vehicle to a different location), and primarily located near airports or busy city areas and often complemented by a website allowing online reservations.

Car rental agencies primarily serve people who have a car that is temporarily out of reach or out of service, for example travellers who are out of town or owners of damaged or destroyed vehicles who are awaiting repair or insurance compensation. Because of the variety of sizes of their vehicles, car rental agencies may also serve the self-moving industry needs, by renting vans or trucks, and in certain markets other types of vehicles such as motorcycles or scooters may also be offered.

Alongside the basic rental of a vehicle, car rental agencies typically also offer extra products such as insurance, global positioning satellite (GPS) navigation systems, entertainment systems, and even such things as mobile phones.

Builders of computer systems often need information about floating-point arithmetic. There are, however, remarkably few sources of detailed information about it. One of the few books on the subject, Floating-Point Computation by Pat Sterbenz, is long out of print. This paper is a tutorial on those aspects of floating-point arithmetic (floating-point hereafter) that have a direct connection to systems building. It consists of three loosely connected parts. The first Section, “Rounding Error,” on page 173, discusses the implications of using different rounding strategies for the basic operations of addition, subtraction, multiplication and division. It also contains background information on the two methods of measuring rounding error, ulps and relative error. The second part discusses the IEEE floating-point standard, which is becoming rapidly accepted by commercial hardware manufacturers. Included in the IEEE standard is the rounding method for basic operations. The discussion of the standard draws on the material in the Section , “Rounding Error,” on page 173. The third part discusses the connections between floating-point and the design of various aspects of computer systems. Topics include instruction set design, optimizing compilers and exception handling.

Health insurance is insurance that pays for medical expenses. It is sometimes used more broadly to include insurance covering disability or long-term nursing or custodial care needs. It may be provided through a government-sponsored social insurance program, or from private insurance companies. It may be purchased on a group basis (e.g., by a firm to cover its employees) or purchased by individual consumers. In each case, the covered groups or individuals pay premiums or taxes to help protect themselves from high or unexpected healthcare expenses. Similar benefits paying for medical expenses may also be provided through social welfare programs funded by the government.

However, it was not until the 15th century that spies were specially trained for their purpose, and not until the 17th century that the word shinobi appeared to define and clearly identify ninjas as a secretive group of agents. Evidence for this can be seen in historical documents, which began to refer to stealthy soldiers as shinobi during the Sengoku period.

Tyrannosaurus rex was one of the largest land carnivores of all time; the largest complete specimen, FMNH PR2081 ("Sue"), measured 12.8 metres (42 ft) long, and was 4.0 metres (13 ft) tall at the hips. Mass estimates have varied widely over the years, from more than 7.2 metric tons (7.9 short tons), to less than 4.5 metric tons (5.0 short tons), with most modern estimates ranging between 5.4 and 6.8 metric tons (6.0 and 7.5 short tons). Although Tyrannosaurus rex was larger than the well known Jurassic theropod Allosaurus, it was slightly smaller than Cretaceous carnivores Spinosaurus and Giganotosaurus.

With only 20 aircraft ultimately built, the costly development phase represented a substantial economic loss. Additionally, Air France and British Airways were subsidised by their governments to buy the aircraft. As a result of the type's only crash (on 25 July 2000), world economic effects arising from the 9/11 attacks, and other factors, operations ceased on 24 October 2003. The last "retirement" flight occurred on 26 November 2003.

Concorde remains an icon of aviation history, and has acquired an unusual nomenclature for an aircraft. In common usage in the United Kingdom, the type is known as "Concorde" rather than "the Concorde" or "a Concorde".

The Ivy League is an athletic conference comprising eight private institutions of higher education in the Northeastern United States. The term is most commonly used to refer to those eight schools considered as a group. The term also has connotations of academic excellence, selectivity in admissions, and social elitism.

The term became official, especially in sports terminology, after the formation of the NCAA Division I athletic conference in 1954, when much of the nation polarized around favorite college teams. The use of the phrase is no longer limited to athletics, and now represents an educational philosophy inherent to the nation's oldest schools. In addition, Ivy League schools are often viewed by the public as some of the most prestigious universities worldwide and are often ranked amongst the best universities in the United States and worldwide.

After the death of his father, Georges Vuitton began a campaign to build the company into a worldwide corporation, exhibiting the company's products at the Chicago World's Fair in 1893. In 1896, the company launched the legendary Monogram Canvas and made the worldwide patents on it. Its graphic symbols, including quatrefoils and flowers (as well as the LV monogram), were based on the trend of using Japanese and Oriental designs in the late Victorian era. The patents later proved to be successful in stopping counterfeiting. In this same year, Georges traveled to the United States, where he toured various cities (such as New York, Philadelphia, and Chicago), selling Vuitton products during the visit. In 1901, the Louis Vuitton Company introduced the Steamer Bag, a smaller piece of luggage designed to be kept inside Vuitton luggage trunks.