What does eosinophile mean?
An eosinophile is a type of white blood cell, more commonly called an eosinophil, that plays a key role in the immune system's defense against parasitic infections and in allergic reactions. The name reflects the cell's defining property: it stains vividly with eosin, a rosy-pink dye introduced in the late nineteenth century that became a staple of laboratory microscopy. Eosinophiles contain granules loaded with inflammatory chemicals, and when their numbers rise above normal — a condition known as eosinophilia — doctors take it as a clue pointing toward asthma, allergies, drug reactions, or intestinal parasites. The word belongs firmly to medical and scientific registers; ordinary speakers rarely encounter it outside a doctor's explanation of a blood test. While "eosinophile" remains understandable, modern medical writing overwhelmingly prefers the shorter spelling "eosinophil," making this longer form a chiefly historical or British variant of the same term.
nounA white blood cell (a type of granulocyte) that stains readily with the acidic dye eosin and is involved in allergic responses and defense against parasitic infections; also called an eosinophil. The word may also refer to any cell or organism that has an affinity for eosin stain.
- A type of white blood cell that stains readily with eosin and participates in immune responses to parasites and allergens.
- Any cell or organism showing an affinity for eosin stain.
"The blood smear showed an elevated number of eosinophiles, suggesting a parasitic infection."
"An abnormally high eosinophile count often points to allergies or a parasitic infection."
"Under the microscope, each eosinophile appeared studded with coarse pink-staining granules."
Standard English plural; also written "eosinophils" under the preferred modern spelling.
"Parasitic infections typically cause a surge of eosinophiles in the bloodstream."
Its name literally means 'eosin-loving' — these cells were named for their eagerness to soak up a rosy pink dye invented in the 1800s.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of eosinophile
The word combines "eosin," the name of the pink dye derived from Greek ēōs meaning "dawn" (chosen because of the dye's dawn-like reddish glow), with the suffix "-phile" from Greek philos, "loving." Thus it literally means "eosin-loving." The term arose in the late nineteenth century following the introduction of aniline dyes into histology. It shares its Greek roots with words such as "philanthropy" and "hemophilia."
Related word forms
How eosinophile is actually used
The spelling "eosinophil" is now strongly preferred in medical literature; "eosinophile" appears mostly in older texts or British usage. It is a technical term confined largely to medicine and laboratory science.
Easily confused with eosinophile
"Eosinophil" is by far the standard modern spelling of the same cell; "eosinophile" is a chiefly older or British variant using the -phile ending.