ENGLISH
REFERENCE

illness

n.
US //ˈɪɫnəs// UK //ˈɪlnəs// ill·ness
  1. 1 a specific disease (n.)
    A2 Elementary Medicine

    a specific disease or period of being sick.

    a specific instance of disease or a period of sickness. Countable in this sense.

    Example

    She missed two weeks of school because of a sudden illness.

    Example

    The doctor struggled to diagnose the mysterious illness that had affected several passengers during the long flight.

    Usage

    Often used with adjectives like 'serious', 'minor', or 'chronic'.
    Pitfall
    He has a long illness.
    He has a chronic illness.

    While 'long' is understandable, 'chronic' or 'prolonged' are the standard adjectives for an illness that lasts a long time.

  2. 2 the state of being sick (n.)
    B1 Intermediate Medicine

    the general state of being unwell or having poor health.

    the general condition of being unhealthy or diseased. Uncountable in this abstract sense.

    Example

    The company provides insurance to help workers during times of illness.

    Example

    Public health initiatives aim to reduce the burden of illness in urban populations through better sanitation and vaccination programmes.

    Usage

    Often used in formal contexts regarding public health or statistics.
Origin

From ill + -ness.

© 2026 English Reference