Distance is a numerical measurement of how far apart objects or points are. In physics or everyday usage, distance may refer to a physical length or an estimation based on other criteria (e.g. "two counties over"). The distance from a point A to a point B is sometimes denoted as
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A
B
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{\displaystyle |AB|}
. In most cases, "distance from A to B" is interchangeable with "distance from B to A". In mathematics, a distance function or metric is a generalization of the concept of physical distance; it is a way of describing what it means for elements of some space to be "close to", or "far away from" each other.
In psychology and social sciences, distance is a non-numerical measurement; Psychological distance is defined as "the different ways in which an object might be removed from" the self along dimensions such as "time, space, social distance, and hypotheticality.
Education is the process of facilitating learning, or the acquisition of knowledge, skills, values, morals, beliefs, and habits. Educational methods include teaching, training, storytelling, discussion and directed research. Education frequently takes place under the guidance of educators; however, learners can also educate themselves. Education can take place in formal or informal settings, and any experience that has a formative effect on the way one thinks, feels, or acts may be considered educational. The methodology of teaching is called pedagogy.
Formal education is commonly divided formally into stages such as preschool or kindergarten, primary school, secondary school and then college, university, or apprenticeship. In most regions, education is compulsory up to a certain age.
There are movements for education reforms, such as for improving quality and efficiency of education towards relevance in students' lives and efficient problem solving in modern or future society at large, or for evidence-based education methodologies. A right to education has been recognized by some governments and the United Nations. Global initiatives aim at achieving the Sustainable Development Goal 4, which promotes quality education for all.A train is a form of rail transport consisting of a series of connected vehicles that generally run along a railroad (or railway) track to transport passengers or cargo (also known as "freight" or "goods"). The word train comes from the Old French trahiner, derived from the Latin trahere meaning 'to pull, to draw'.Motive power for a train is provided by a separate locomotive or individual motors in a self-propelled multiple unit. The term "engine" is often used as an alternative to locomotive. Although historically steam propulsion dominated, the most common types of locomotive are diesel and electric, the latter supplied by overhead wires or additional rails. Trains can also be hauled by horses, pulled by engine or water-driven cable or wire winch, run downhill using gravity, or powered by pneumatics, gas turbines or electric batteries.
The track usually consists of two running rails with a fixed spacing, which may be supplemented by additional rails such as electric conducting rails ("third rail") and rack rails. Monorails and maglev guideways are also occasionally used.Passenger trains include passenger-carrying vehicles and can often be very long and fast. High-speed rail systems began expanding rapidly in the late 20th century, and this remains a major subject of further development. The term "light rail" is sometimes used to refer to a modern tram system, but it may also mean an intermediate form between a tram and a train, similar to a heavy rail rapid transit system.
Freight (goods) trains use freight cars (or wagons/trucks) to transport goods or materials (cargo). It is possible to carry passengers and freight in the same train using a mixed consist.
Rail cars and machinery that are used for the maintenance and repair of tracks, are termed "maintenance of way" equipment; these may be assembled into maintenance of way trains. Similarly, dedicated trains may be used to provide support services to stations along a train line, such as garbage or revenue collection.