Symmetry

1. Symmetry is the concept that the properties of particles such as atoms and molecules remain unchanged after being subjected to a variety of symmetry transformations or “operations”.
2. In physics, a symmetry of a physical system is a physical or mathematical feature of the system (observed or intrinsic) that is preserved or remains unchanged under some transformation.

The application of symmetry to physics leads to the important conclusion that certain physical laws, particularly conservation laws, governing the behaviour of objects and particles are not affected when their geometric coordinates – including time, when it is considered as a fourth dimension – are transformed by means of symmetry operations. The physical laws thus remain valid at all places and times in the universe. In particle physics, considerations of symmetry can be used to derive conservation laws and to determine which particle interactions can take place and which cannot (the latter are said to be forbidden). Symmetry also has applications in many other areas of physics and chemistry – for example, in relativity and quantum theory, crystallography, and spectroscopy. Crystals and molecules may indeed be described in terms of the number and type of symmetry operations that can be performed on them. The quantitative discussion of symmetry is called group theory.

Sources:

Merriam-Webster's Collegiate® Dictionary, Eleventh Edition https://www.merriam-webster.com/dictionary

Словник Cambridge Dictionary https://dictionary.cambridge.org/

Britannica https://www.britannica.com/science/