Projection or projections may refer to:

Physics

Projection (physics) The vector projection (also known as the vector component or vector resolution) of a Vector (geometry), vector on (or onto) a nonzero vector is the orthogonal projection of onto a straight line parallel to . The projection of onto is often ...

, the action/process of light, heat, or sound reflecting from a surface to another in a different direction * The display of images by a

projector A projector or image projector is an optical device that projects an image (or moving images) onto a surface, commonly a projection screen. Most projectors create an image by shining a light through a small transparent lens, but some newer type ...

Optics, graphics, and cartography

Map projection In cartography, a map projection is any of a broad set of Transformation (function) , transformations employed to represent the curved two-dimensional Surface (mathematics), surface of a globe on a Plane (mathematics), plane. In a map projection, ...

, reducing the surface of a three-dimensional planet to a flat map *

Graphical projection A 3D projection (or graphical projection) is a design technique used to display a three-dimensional (3D) object on a two-dimensional (2D) surface. These projections rely on visual perspective and aspect analysis to project a complex object f ...

, the production of a two-dimensional image of a three-dimensional object

Chemistry

Fischer projection In chemistry, the Fischer projection, devised by Emil Fischer in 1891, is a two-dimensional representation of a three-dimensional organic molecule by projection. Fischer projections were originally proposed for the depiction of carbohydrates a ...

, a two-dimensional representation of a three-dimensional organic molecule *

Haworth projection In chemistry, a Haworth projection is a common way of writing a structural formula to represent the cyclic structure of monosaccharides with a simple three-dimensional perspective. A Haworth projection approximates the shapes of the actual mole ...

, a way of writing a structural formula to represent the cyclic structure of monosaccharides * Natta projection, a way to depict molecules with complete stereochemistry in two dimensions in a skeletal formula *

Newman projection A Newman projection is a drawing that helps visualize the 3-dimensional structure of a molecule. This projection most commonly sights down a carbon-carbon bond, making it a very useful way to visualize the stereochemistry of alkanes. A Newman pro ...

, a visual representation of a chemical bond from front to back

Mathematics

Projection (mathematics) In mathematics, a projection is an idempotent mapping of a set (or other mathematical structure) into a subset (or sub-structure). In this case, idempotent means that projecting twice is the same as projecting once. The restriction to a subspa ...

, any of several different types of geometrical mappings **

Projection (linear algebra) In linear algebra and functional analysis, a projection is a linear transformation P from a vector space to itself (an endomorphism) such that P\circ P=P. That is, whenever P is applied twice to any vector, it gives the same result as if it ...

, a linear transformation from a vector space to itself such that **

Projection (set theory) In set theory, a projection is one of two closely related types of functions or operations, namely: * A set-theoretic operation typified by the jth projection map, written \mathrm_j, that takes an element \vec = (x_1,\ \dots,\ x_j,\ \dots,\ x_k) ...

, one of two closely related types of functions or operations in set theory ** Projection (measure theory), use of a projection map in measure theory **

3D projection A 3D projection (or graphical projection) is a Design, design technique used to display a three-dimensional (3D) object on a two-dimensional (2D) surface. These projections rely on perspective (graphical), visual perspective and aspect analysi ...

, any method of mapping three-dimensional points to a two-dimensional plane **

Vector projection The vector projection (also known as the vector component or vector resolution) of a vector on (or onto) a nonzero vector is the orthogonal projection of onto a straight line parallel to . The projection of onto is often written as \oper ...

, orthogonal projection of a vector onto a straight line **

Projection (relational algebra) In relational algebra, a projection is a unary operation written as \Pi_( R ), where R is a relation and a_1,...,a_n are attribute names. Its result is defined as the set obtained when the components of the tuples in R are restricted to the se ...

, a type of unary operation in relational algebra *

Projection method (fluid dynamics) In computational fluid dynamics, the projection method, also called Chorin's projection method, is an effective means of numerically solving time-dependent incompressible fluid-flow problems. It was originally introduced by Alexandre Chorin in ...

, means of numerically solving time-dependent incompressible fluid-flow problems

Biology

* Projection areas, areas of the brain where sensory processing occurs *

Projection fiber Projection fibers consist of efferent and afferent fibers uniting the cortex with the lower parts of the brain and with the spinal cord. In human neuroanatomy, bundles of axons (nerve fibers) called nerve tracts, within the brain, can be cate ...

, in neuroscience, white matter fibers that connect the cortex to the lower parts of the brain or the spinal cord

Linguistics

* Projection (linguistics), grammatical trait inheritance from a head to a phrasal category *

Projection principle In linguistics, the projection principle is a stipulation proposed by Noam Chomsky as part of the phrase structure component of Generative grammar, generative-transformational grammar. The projection principle is used in the derivation of phrases ...

in syntax * Projection of

presupposition In linguistics and philosophy, a presupposition is an implicit assumption about the world or background belief relating to an utterance whose truth is taken for granted in discourse. Examples of presuppositions include: * ''Jane no longer writes ...

s in linguistics

Arts and entertainment

* "Projections" (''Star Trek: Voyager''), an episode of the television series ''Star Trek: Voyager'' * ''Projections'' (The Blues Project album), 1966 * ''Projections'' (John Handy album), 1968 * ''Projections'' (film), 2013 Croatian film

Other uses

Projection (alchemy) Projection was the ultimate goal of Western alchemy. Once the philosopher's stone or powder of projection had been created, the process of projection would be used to transmute a lesser substance into a higher form; often lead into gold. Typ ...

, process in Alchemy * ''Projections'' (journal), an interdisciplinary academic journal related to cinema and visual media *

Power projection Power projection (or force projection or strength projection) in international relations is the capacity of a state to deploy and sustain forces outside its territory. The ability of a state to project its power into an area may serve as an eff ...

, the capacity of a state to implement policy by means of force, or the threat thereof *

Psychological projection Psychological projection is a defence mechanism of alterity concerning "inside" ''content'' mistaken to be coming from the "outside" Other. It forms the basis of empathy by the projection of personal experiences to understand someone else's su ...

, or "Freudian projection", a defense mechanism in which one attributes to others one's own unacceptable or unwanted attributes, thoughts, or emotions *

Social projection In social psychology, social projection is the psychological process through which an individual expects behaviors or attitudes of others to be similar to their own. Social projection occurs between individuals as well as across ingroup and outgr ...

, a cognitive bias that leads people to believe others are similar to themselves *

Forecasting Forecasting is the process of making predictions based on past and present data. Later these can be compared with what actually happens. For example, a company might Estimation, estimate their revenue in the next year, then compare it against the ...

, making predictions of the future based on past and present data *

Population projection A population projection, in the field of demography, is an estimate of a future population. It is usually based on current population estimates derived from the most recent census plus a projection of possible changes based on assumptions of future ...

, in the field of demography, an estimate of a future population