Concept of an expanding universe whose average density remains constant, matter being continuously created throughout it to form new stars and galaxies at the same rate that old ones recede from sight. A steady-state universe has no beginning or end, and its average density and arrangement of galaxies are the same as seen from every point. Galaxies of all ages are intermingled. The theory was first put forward by William Macmillan (1861–1948) in the 1920s and modified by Fred Hoyle to deal with problems that had arisen in connection with the big-bang model. Much evidence obtained since the 1950s contradicts the steady-state theory and supports the big-bang model.

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In physics, the combination of two theories of particle physics into a single framework to describe all interactions of subatomic particles except those due to gravity (see gravitation). The two theories, the electroweak theory and the theory of quantum chromodynamics, describe the interactions between particles in terms of the exchange of intermediary particles. The model has proved highly accurate in predicting certain interactions, but it does not explain all aspects of subatomic particles. For example, it cannot say how many particles there should be or what their masses are. The search goes on for a more complete theory, and in particular a unified field theory describing the strong, weak, and electromagnetic forces.

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Automobile built by the Ford Motor Co. from 1908 until 1927, the first widely affordable mass-produced car. Assembly-line production methods introduced by Henry Ford in 1913 enabled the price of this five-seat touring car to drop from $850 in 1908 to $300 in 1925. Over 15 million Model T's were built. The car was offered in several body styles, all mounted on a standard chassis. Various colors were initially available, but after 1913 its sole color was black. It was replaced by the popular Model A in 1928.

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A model is a pattern, plan, representation (especially in miniature), or description designed to show the main object or workings of an object, system, or concept. Model may also refer to:

Abstractions, concepts, and theories:

• Model (abstract), an abstraction or conceptual object used in the creation of a predictive formula
• Causal model, an abstract model that uses cause and effect logic
• Mathematical model, an abstract model that uses mathematical language
• Statistical model, in applied statistics, a parameterized set of probability distributions
• Model theory, study of the representation of mathematical concepts
• Meta-modeling, a model of a model
• Computer model, a computer program which attempts to simulate an abstract model of a particular system
• Data model, a description of the structure of a database
• Scientific modelling, the process of generating abstract models
• The Standard Model, the theory in particle physics which describes certain fundamental forces and particles
• Model building (particle physics), the construction of new models beyond the Standard Model in particle physics
• Molecular modelling, methods and techniques to model the behaviour of molecules
• Geologic modelling, the applied science of creating computerized models of geologic features
• A pre-clinical development model of a biological process, used in biological or medical research
• Model Driven Engineering, the systematic use of models in engineering
• Morphological modelling, a problem-solving technique used for problems with which causal modelling does not function well
• Similitude (model), in engineering, used in the scientific testing of physical models
• Working Model, engineering software
• Model (economics), a theoretical construct representing economic processes
• Model (macroeconomics), an economic model representing a national or regional economy
• Business model, a framework expressing the business logic of a firm
• Model-view-controller, an architectural pattern in software engineering
• Toy model, a simplified system that illustrates or exhibits the same behaviour as the more complex, general system

As representations of objects:

• Model (physical), a physical representation of an object
• Solid modeling, study of unambiguous representations of the solid parts of an object
• Scale model, a replica or prototype of an object
• Model building, a hobby centered around construction of material replicas
• 3D model, a 3D polygonal representation of an object, usually displayed with a computer

In human and animal behavior

• An organism (or set of signals originating from it) that is mimicked by another.
• Mental model, a person's cognitive representation of an idea or thought process
• Modeling (NLP), a process in neuro-linguistic programming
• Modelling (psychology), learning by imitating or observing a person's behavior
• Role model, a person who serves as a behavioural or moral example to others

In occupations:

• Model (person), a person employed to display his or her looks or something such as a commercial product, e.g., a fashion model (see also supermodel). Subcategories include:
• Model (art), a person who poses to be depicted in art, for example in art school
• Promotional model, a person who interacts with consumers to draw attention to and often inform them about a product
• Fetish model, a model who wears the clothing and/or devices of sexual fetishes

In history and culture:

• Walther Model, German field marshal in World War II
• Movement for Democracy in Liberia, MoDeL
• Models (band), an alternative rock group from Australia
• Model (manhwa), a manhwa series by Lee So Young
• Models (film), a 1999 film by Ulrich Seidl
• "Model," a song by Avail from their 1994 album Dixie

In lighting:

• Modeling (lighting) means how a key light reveals the three-dimensional form of a subject
• Modeling light, a continuous light source that visualizes the effect of a photographic flash

In geography:

• Model, Colorado, an unincorporated town in the United States
• Model (Poland) - a village in Poland in Masovia Voivodeship in Gostyniński county in Pacyna commune

See also

• Domain-specific modelling (DSM)
• General-purpose modeling (GPM)
• MTL
• Modeling languages
• MOF (for OMG software engineering models)
• Non-quantified modelling
• Unified Modeling Language (UML)
• Systems Modeling Language (SysML)
• Scientific modelling
• Software for molecular mechanics modeling