Understanding systems

A whole systems approach to obesity is like a bicycle. It is made up of many separate parts and can only work when all parts work together. Learn more about this in #PHEHealthMatters: https://t.co/PAe3yoQKN2 pic.twitter.com/U7TgJw3Nir

— Public Health England (@PHE_uk) July 28, 2019

A system is made up of separate parts.
No single part operates the system alone.
All parts must work together. The function of a system is different from the sum of its parts.