Find over 25,000 psychological definitions


immune system

a complex system in vertebrates that helps protect the body against pathological effects of foreign substances (antigens), such as viruses and bacteria. The organs involved include the bone marrow and thymus, in which lymphocytes—the principal agents responsible for specific immune responses—are produced, together with the spleen, lymph nodes, and other lymphoid tissues and various chemicals (e.g., cytokines) that mediate the immune response. The immune system interacts with both the nervous system and the endocrine system. See also psychoneuroimmunology.

Browse dictionary by letter

a b c d e f g h i j k l m n o p q r s t u v w x y z

Psychology term of the day

January 31st 2025

aromatherapy

aromatherapy

n. a type of therapy purported to improve psychological and physical health through the use of selected essential oils extracted from seeds, herbs, flowers, fruits, and trees. The fragrances of these oils are inhaled or the oils themselves are applied topically, using compresses, baths, or massages, in an effort to induce relaxation, reduce stress and emotional distress, and enhance well-being. Evidence supporting the effectiveness of aromatherapy is largely inconclusive. See also complementary and alternative medicine.