What does eosinophil mean?
An eosinophil is a type of white blood cell — specifically a granulocyte — whose granules stain vividly pink-red when treated with eosin, an acidic dye. The name derives from Eos, the Greek goddess of dawn, reflecting the rosy hue the cells take on under the microscope. Eosinophils form part of the innate immune system: they help destroy multicellular parasites such as worms, and they contribute to the inflammation seen in allergies, asthma, and certain skin conditions. In clinical practice, doctors often measure a patient's 'eosinophil count'; an abnormally high number, called eosinophilia, may indicate a parasitic infection, an allergic disorder, or another underlying illness, while very low counts rarely cause symptoms. The word is chiefly encountered in medicine, haematology, and pathology, appearing in terms like 'eosinophilic asthma'. Its plural is 'eosinophils', and its adjective form is 'eosinophilic'. Though technical, it is a useful word for anyone reading medical reports or discussing immune health.
nounA type of white blood cell (a granulocyte) characterized by granules that stain readily with the acidic dye eosin; eosinophils play a key role in the immune response to parasites and are involved in allergic reactions and asthma.
- A white blood cell whose granules stain with eosin, involved in defence against parasites and in allergic inflammation.
"The blood test revealed an elevated eosinophil count, suggesting a parasitic infection or allergic reaction."
"A high eosinophil level in her bloodwork pointed the doctors toward an underlying allergy."
"Eosinophils congregate in tissues infected with helminths, releasing toxic proteins to destroy the invaders."
Standard English plural; by far the most common form in practice, since these cells are usually discussed in numbers.
"Tissue biopsies showed numerous eosinophils infiltrating the lining of the gut."
Named after 'eosin', a rose-pink dye that takes its name from Eos, the Greek goddess of dawn — so these cells are literally 'dawn-loving' because they blush pink under the microscope.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of eosinophil
The word 'eosinophil' was coined in the late 19th century from 'eosin', a red-pink dye named after Eos, the Greek goddess of dawn (from Greek ēōs, meaning dawn), combined with the suffix '-phil' from Greek 'philein', to love — hence 'eosin-loving', describing cells that readily take up the stain. It belongs to a family of staining-based cell names alongside 'basophil' ('base-loving') and 'neutrophil' ('neutral-loving'). Related words sharing the root include 'eosin' itself, 'eosinophilia', and other '-phil' formations such as 'haemophilia'.
Related word forms
How eosinophil is actually used
Primarily used in medical, immunological, and laboratory contexts. The adjective form is 'eosinophilic' and the condition of excess eosinophils is 'eosinophilia'. Plural is 'eosinophils'.
Easily confused with eosinophil
Basophils stain with basic dyes rather than the acidic dye eosin, and they release histamine, whereas eosinophils target parasites and mediate allergic responses.