Imaginary unitThe imaginary unit or unit imaginary number (i) is a solution to the quadratic equation . Although there is no real number with this property, i can be used to extend the real numbers to what are called complex numbers, using addition and multiplication. A simple example of the use of i in a complex number is . Imaginary numbers are an important mathematical concept; they extend the real number system to the complex number system , in which at least one root for every nonconstant polynomial exists (see Algebraic closure and Fundamental theorem of algebra).
Word orderIn linguistics, word order (also known as linear order) is the order of the syntactic constituents of a language. Word order typology studies it from a cross-linguistic perspective, and examines how different languages employ different orders. Correlations between orders found in different syntactic sub-domains are also of interest. The primary word orders that are of interest are the constituent order of a clause, namely the relative order of subject, object, and verb; the order of modifiers (adjectives, numerals, demonstratives, possessives, and adjuncts) in a noun phrase; the order of adverbials.
Axiom of extensionalityIn axiomatic set theory and the branches of logic, mathematics, and computer science that use it, the axiom of extensionality, or axiom of extension, is one of the axioms of Zermelo–Fraenkel set theory. It says that sets having the same elements are the same set. In the formal language of the Zermelo–Fraenkel axioms, the axiom reads: or in words: Given any set A and any set B, if for every set X, X is a member of A if and only if X is a member of B, then A is equal to B.
History of the automobileDevelopment of the automobile started in 1672 with the invention of the first steam-powered vehicle, which led to the creation of the first steam-powered automobile capable of human transportation, built by Nicolas-Joseph Cugnot in 1769. Inventors began to branch out at the start of the 19th century, creating the de Rivas engine, one of the first internal combustion engines, and an early electric motor. Samuel Brown later tested the first industrially applied internal combustion engine in 1826.
Slow FoodSlow Food is an organization that promotes local food and traditional cooking. It was founded by Carlo Petrini in Italy in 1986 and has since spread worldwide. Promoted as an alternative to fast food, it strives to preserve traditional and regional cuisine and encourages farming of plants, seeds, and livestock characteristic of the local ecosystem. It promotes local small businesses and sustainable foods. It also focuses on food quality, rather than quantity. It was the first established part of the broader slow movement.
Peak carPeak car (also peak car use or peak travel) is a hypothesis that motor vehicle distance traveled per capita, predominantly by private car, has peaked and will now fall in a sustained manner. The theory was developed as an alternative to the prevailing market saturation model, which suggested that car use would saturate and then remain reasonably constant, or to GDP-based theories which predict that traffic will increase again as the economy improves, linking recent traffic reductions to the Great Recession of 2008.
Personal rapid transitPersonal Rapid Transit (PRT), also referred to as podcars or guided/railed taxis, is a public transport mode featuring small low-capacity automated vehicles operating on a network of specially built guideways. PRT is a type of automated guideway transit (AGT), a class of system which also includes larger vehicles all the way to small subway systems. In terms of routing, it tends towards personal public transport systems. PRT vehicles are sized for individual or small group travel, typically carrying no more than three to six passengers per vehicle.
