System: Set of interacting or interdependent components

These things can be real or imaginary. Systems can be man-made things like a car engine or natural things like a star system. Systems can also be concepts made by people to organize ideas.

A subsystem is a system that is part of some larger system. For example, in computer networking, a disk subsystem is a part of a computer system.

• A system is a group of things that connect and form some kind of coherent whole.

One of the founders of physiology, Claude Bernard, took a big step when he noticed that the internal systems of the body tend to keep things the same even if they are disturbed. He called the functions which keep system stable as homeostasis. This led towards the ideas of error-correction, feedback and regulation. These are all typical of systems which have some kind of goal and can adjust their behaviour so as to correct errors.

The Solar System is an example of a system. The Solar System includes the Sun and the eight planets, as well as the moons of those planets. These and other members are linked by gravity and by their history as a planetary system.

There are many kinds of systems. The key is that the elements of a system work together as a whole whilst still keeping their own identity. This is why planetary systems and body systems are good examples. They work together but have their own separate identity.

• Systems in a living person, such as digestive system, nervous system, and so on. These systems operate so as to keep the body's physiology going within limits.
• Systems of life, such as life cycle, carbon cycle, or ecosystem
• Systems in science, such as the solar system
• Any mechanical or electrical gadgets where parts work together to keep the output within certain limits. A thermostat is the classic example of this.

• Systems theory
• Systems science
• Cybernetics