What does 'mental illness' really mean?

Most of us have heard the terms mental illness or mental disorder or psychiatric condition. While these terms are generally used to describe a wide range of different conditions, what they all have in common is that they all affect a person’s emotions, thoughts and behaviours — basically how a person sees themselves, sees the world around them, and how they interact within their environment. The key difference to know between 'having a bad day' and having a 'mental health issue', lies in both the duration and magnitude that the impacts have on your life and behaviours. It is important to note that there are many different kinds of mental diseases, just as there are many different kinds of physical diseases.