Model
A model is an informative representation of an object, person or system. The term originally denoted the plans of a building in late 16th-century English, and derived via French and Italian ultimately from Latin "modulus", a measure. Models can be divided into physical models (e.g. a model plane) and abstract models (e.g. mathematical expressions describing behavioural patterns). Abstract or conceptual models are central to philosophy of science, as almost every scientific theory effectively embeds some kind of model of the physical or human sphere. In commerce, "model" can refer to a specific design of a product as displayed  in a catalogue or show room (e.g. Ford Model T), and by extension to the sold product itself. Types of models include: Physical model. A physical model (most commonly referred to simply as a model but in this context distinguished from a conceptual model) is a smaller or larger physical copy of an object. The object being modelled may be small (for example, an atom) or large (for example, the Solar System). In some sense, a physical model "is always the reification of some conceptual model; the conceptual model is conceived ahead as the blueprint of the physical one", which  is then constructed as conceived. The geometry of the model and the object it represents are often similar in the sense that one is a rescaling of the other; in such cases, the scale is an important characteristic. However, in many cases the similarity is only approximate or even intentionally distorted. Sometimes the distortion is systematic (e.g., a fixed scale horizontally and a larger fixed scale vertically when modelling topography of a large area, as opposed to a model of a smaller mountain region, which may well use the same scale horizontally and vertically, showing the true slopes). Physical models  allow visualization, from examining the model, of information about the thing the model represents. A model can be a physical object such as an architectural model of a building. Uses of an architectural model include visualization of internal relationships within the structure or external relationships of the structure to the environment. Other uses of models in this sense are as toys. Instrumented physical models are an effective way of investigating fluid flows for Engineering design. Physical models are often coupled with Computational Fluid Dynamics models to optimize the design of equipment and processes. This includes external flow such as around  buildings, vehicles, people, or hydraulic structures. Wind Tunnel and Water Tunnel testing is often used for these design efforts. Instrumented physical models can also examine internal flows, for the design of ductwork systems, pollution control equipment, food processing machines, and mixing vessels. Transparent flow models are used in this case to observe the detailed flow phenomenon. These models are scaled in terms of both geometry and important forces, for example, using Froude number or Reynolds number scaling (see Similitude). A physical model of something large is usually smaller, and of something very small is larger. A physical model of something  that can move, like a vehicle or machine, may be completely static, or have parts that can be moved manually, or be powered. A physical model may show inner parts that are normally not visible. The purpose of a physical model on a smaller scale may be to have a better overview, for testing purposes, as hobby or toy. The purpose of a physical model on a larger scale may be to see the structure of things that are normally too small to see properly or to see at all, for example, a model of an insect or of a  molecule. A physical model of an animal shows the animals physical composition without it walking or flying away, and without danger, and if the real animal is not available. A soft model of an animal is popular among children and some adults as cuddly toy. A model of a person may e.g. be a doll, a statue, and in fiction a robotic humanoid, e.g. the mechas in the movie "A.I.". A model is a 3D alternative for a 2D representation such as a drawing or photograph, or in the case of a globe, a 3D, undistorted alternative for a flat  world map. Examples. Some of the examples of Physical models: Conceptual model. A conceptual model is a theoretical representation of a system, e.g. a set of equations attempting to describe the workings of the atmosphere for the purpose of weather forecasting. Conceptual models may be a representation of a system. It consists of concepts used to help people know, understand, or simulate a subject the model represents. The term may refer to models that are formed after a conceptualization or generalization process. Conceptual models are often abstractions of things in the real world, whether physical or social. Semantic studies are  relevant to various stages of concept formation. Semantics is basically about concepts, the meaning that thinking beings give to various elements of their experience.