" For a detailed description of the differences between fermions and bosons, see the article on identical particles. In the Standard Model, the theory of the electroweak interaction (which describes the weak and electromagnetic interactions) is combined with the theory of quantum chromodynamics . All of these theories are gauge theories, meaning that they model the forces between fermions by coupling them to bosons which mediate (or "carry") the forces. The Lagrangian of each set of mediating bosons is invariant under a transformation called a gauge transformation, so these mediating bosons are referred to as gauge bosons. The bosons in the Standard Model are: Unsolved problems in physics: Parameters in the Standard Model: What gives rise to the Standard Model of particle physics? Why do its particle masses and coupling constants possess the values we have measured? Does the Higgs boson predicted by the model really exist? Why are there three generations of particles in the Standard Model? Is the Standard Model reality, a good approximation to reality, or fatally flawed? Photons, which mediate the electromagnetic interaction. W and Z bosons, which mediate the weak nuclear force Eight species of gluons, which mediate the strong nuclear force. Six of these gluons are labelled as pairs of "colors" and "anti-colors" (for example, a gluon can carry "red" and "anti-green". Car Custom Model) The other two species are a more complex mix of colors and anti-colors. The Higgs bosons, which induce spontaneous symmetry breaking of the gauge groups and are responsible for the existence of inertial mass. "

" (Eds. ) Professional knowledge management; LNCS 3782 Springer Verlag; 2005. Models as people artist model — in art school modeling, a person who poses for purposes of art. model — person whose occupation is to display clothing (eg. a "fashion model") or other personal items of artistic or aesthetic value, and who is often physically attractive; a model who attains celebrity status or is otherwise widely known is said to be a "supermodel". promotion model— promotes a product or service role model — person who acts as a behavioural or moral example to others. Models as physical objects physical model — physical representation of an object; in engineering, similitude is used in the scientific testing of physical models. 2005 Car Model scale model — a replica or prototype of an object built as a hobby or for research. a particular version of a series of vehicles produced by an automobile manufacturer is known as a model. "