These are terms defined by the Association of British Insurers (ABI) which insurers must adhere to.
A chronic condition is defined as one that is long term and requires ongoing monitoring and treatment. It cannot be cured but it can be alleviated. It is likely to be life-long and requires you to be specially trained on how to deal with it. Examples of chronic conditions include:
Pre-existing conditions are those which you have had prior to taking out a health insurance policy, usually 5 years beforehand. These are conditions to which you have received advice, medication and/or treatment. These include the above mentioned and also include: