Defining Health, Illness, Disease & Well-being
Why Definitions Matter
In health and social care, precise language is essential. The words “health”, “illness”, “disease” and “well-being” are used by practitioners every day — but they do not all mean the same thing. The exam unit requires you to know four specific definitions, each drawn from a named authoritative source. These definitions are not interchangeable, and only an accurate distinction between them is credited. This lesson covers each definition in turn, explains its source, and explores the interpretive layers that the exam also assesses.
Health — The WHO Definition
The most widely used definition of health comes from the World Health Organization (WHO). The WHO defines health as “a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity.” This definition was established in 1948 and remains the standard reference point for practitioners and policymakers.
Three features of this definition are particularly important for the exam. First, it is holistic — it covers physical, mental and social dimensions, not just the physical body. Second, it goes beyond the absence of disease: a person may be free from identifiable illness but still not be healthy if their mental or social well-being is poor. Third, it uses the phrase “complete” well-being, which implies a high standard — a standard that some argue is rarely achievable in practice.
The WHO (1948) defines health as: “a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity.” The key phrase is not merely the absence of disease — health is a positive state, not just the lack of illness.
Illness — A Personal Experience
While the WHO definition of health is a professional, objective standard, illness is defined quite differently. Drawing on the British Medical Journal, the specification frames illness as the feeling or experience of ill health — a subjective state that is personal to the individual. This is a crucial distinction: illness is what a person feels, not what a test detects.
The significance of this definition is illustrated by two scenarios. First, illness without disease: a person may feel genuinely unwell — fatigued, in pain, anxious — but no physical cause can be found by medical tests. The person is experiencing illness even though no disease is present. Conditions such as medically unexplained symptoms, chronic fatigue syndrome or certain forms of chronic pain fall into this category. Second, the reverse is also possible: a person may have a diagnosed disease (for example, early-stage hypertension) but feel completely well in themselves. In that case, disease is present without the individual experiencing illness.
In a care setting, a practitioner who only acts when a medically confirmed disease is present may fail to support individuals experiencing genuine illness. A person who says they feel exhausted, anxious and unable to cope deserves to be taken seriously even if blood tests come back clear. Equally, a person with a confirmed chronic condition may not feel “ill” on a daily basis and may not want to be treated as unwell. Person-centred care requires practitioners to respond to both the objective condition and the subjective experience of health.
Disease — Signs and Symptoms
Disease is defined by the specification as a condition characterised by specific signs and symptoms. Unlike illness, which is subjective, disease is an objective, clinically identifiable state. Signs are what a practitioner can observe or measure — a rash, an elevated white blood cell count, a raised temperature. Symptoms are what the patient reports feeling — pain, breathlessness, nausea. A disease can typically be named (for example, pneumonia, type 2 diabetes, multiple sclerosis) and diagnosed through clinical assessment or testing.
It is important to remember that an individual can have a disease without experiencing illness (as in the early-stage hypertension example above), and can experience illness without having a diagnosable disease. This distinction matters — knowing only the general meaning of each word is not enough. You need to be able to explain the specific conceptual difference and give an example that illustrates it.
Illness is the personal, subjective experience of feeling unwell — you can have illness without disease. Disease is an objective, clinically identified condition with specific signs and symptoms — you can have disease without experiencing illness. The two do not always go together.
Well-being — More Than Feeling Fine
The fourth definition — well-being — draws on Psychology Today’s definition. Well-being is described as being happy, healthy and thriving, with good mental health, high life satisfaction, a sense of purpose, and the ability to manage stress. Like the WHO definition of health, well-being is a broad, positive concept — it is about flourishing, not merely the absence of problems.
Well-being differs from health in that it places greater emphasis on the subjective sense of thriving. A person can be medically healthy in the WHO sense but still have low well-being if they feel their life lacks purpose or if they are chronically stressed. This distinction is relevant in care settings: practitioners promoting well-being are not just treating illness or disease — they are supporting individuals to flourish and find meaning.
A holistic view of health recognises that what it means to be “healthy” or to have “well-being” is not universal. These concepts vary between cultures (some cultures prioritise collective harmony over individual health; others integrate spiritual health into their understanding of well-being), across time (historical understandings of health were very different from today’s biomedical model — Victorian medicine did not recognise mental illness in the same way), and across life stages (a 3-year-old’s well-being is largely about attachment and play; a 75-year-old’s well-being may be more about autonomy, social connection and freedom from pain). Practitioners who appreciate this variation are better placed to provide genuinely person-centred care.