There is no concrete definitive definition of stress, because knowledge within this area is constantly evolving. The term is ubiquitous but its meaning is rather an unknown quantity. Definitions of the term ‘stress,’ differ depending on the source, but most of us consider ourselves to have experienced stress. Indeed, with our fast-paced lifestyles and increasing work demands, stress has become endemic and how we manage stress is crucial to our happiness and well-being. 
 
In the eighteenth century and earlier what we might today call stress was often referred to as “passions,” such as nerves and hysteria, and used as explanations for various illnesses. Scientists of the time highlighted the faster pace of life and the subsequent impact on health. Even in the nineteenth century there were concerns that our human nervous systems were not well-adapted to cope with increasingly complex modern lives. During this period it became a common belief that the stresses and strains of life could bring about mental disease. This belief is still commonly held by many.

One of the most commonly accepted modern definitions is that,

Stress is a condition or feeling experienced when a person perceives that demands exceed the personal and social resources the individual is able to mobilise.

Lazarus and Folkman define stress in a similar tack as

A particular relationship between the person and the environment that is appraised by the person as taxing or exceeding his or her resources and endangering his or her well-being.

If individuals feel they cannot cope with expectations or demands required of them, they experience stress. Coping means balancing the pressures placed on you with your capabilities and the resources available to you.

Although stress is often linked to excessive demands, it can also be caused by having limited demands, leading people to experience boredom and a sense of being undervalued.

It’s important to remember that not all stress is bad. Most individuals require a level of pressure in order to succeed and remain motivated. This is often referred to as positive stress. Challenge energises us and when we meet a challenge our well-being is increased, but when this transforms into a situation where demands cannot be met and exhaustion prevails, we experience chronic stress.