noun

• A group or set of related things that operate together as a complex whole.
  "WIPO [the World Intellectual Property Organization] reported that China had 17 of the top 20 academic organizations filing for AI-related patents. It noted China was especially strong in the fast-growing area of "deep learning." This is a machine learning method that includes speech and facial recognition systems."
• A group or set of related things that operate together as a complex whole.
  "The method of solving systems of equations by matrices that we will look at is based on procedures involving equations that we are familiar with from previous mathematics courses. The main idea is to reduce a given system of equations to another simpler system that has the same solutions."
• A group or set of related things that operate together as a complex whole.
  "To notate music that is played on a piano or is played by different musicians on various instruments, one often uses several staves to notate the various musical voices. A single vertical line drawn to the left of multiple staves creates a staff system, which indicates that the music on all staves is to be played simultaneously. A bracket is an additional vertically aligned symbol joining staves. This symbol shows groupings of instruments that function as a unit, such as the string section of an orchestra[…]."
• A group or set of related things that operate together as a complex whole.
  "the digestive system  the nervous system"