What does amyloid mean?
Amyloid is a term from medicine and biochemistry describing an abnormal, insoluble protein material that builds up in the tissues and organs of the body. These fibrous deposits — known as amyloid fibrils — are the hallmark of a group of disorders called amyloidoses, and they are also central to neurodegenerative disease: clumps of beta-amyloid form the plaques found in the brains of people with Alzheimer's disease. The name reflects the word's history: coined in the nineteenth century from Greek roots meaning 'starch-like', because early chemists observed that the substance stained with iodine in the same way starch does. Today the original chemical sense is largely historical, and 'amyloid' is understood almost entirely through its medical meaning. It appears almost exclusively in scientific writing, clinical reports, and health journalism, where phrases such as 'amyloid plaque' and 'amyloid fibrils' are standard. Its prominence in Alzheimer's research has made it one of the most recognisable terms in modern medicine.
nounA starchy or starch-like substance; in modern medicine, an abnormal fibrous protein deposit that accumulates in tissues and organs and is associated with diseases such as Alzheimer's.
- In medicine and biology: an abnormal, insoluble fibrous protein aggregate that accumulates extracellularly in tissues, characteristic of amyloidosis and of the plaques seen in Alzheimer's disease.
- In older chemistry/pathology: a starch-like or cellulose-like substance, so named because it stains blue-black with iodine like starch.
"The autopsy revealed widespread deposits of amyloid in the patient's kidneys."
"Imaging showed significant beta-amyloid accumulation in regions of the brain associated with memory."
"Under the microscope, the tissue stained positive for amyloid, confirming a diagnosis of amyloidosis."
Usually treated as an uncountable mass noun ('amyloid'); the plural appears mainly when referring to distinct types or instances of amyloid proteins.
"Several different amyloids have been linked to human disease."
The word 'amyloid' literally means 'starch-like' — but in the brain, these sticky protein clumps are now the most famous suspects behind Alzheimer's disease.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of amyloid
The word 'amyloid' derives from the Greek 'amylon', meaning starch, combined with the suffix '-oid', meaning 'resembling'. It was introduced in the nineteenth century by German pathologists who noticed that certain tissue deposits stained blue-black with iodine, just as starch does, and so named them 'starch-like'. Related English words sharing the same Greek root include 'amylase', 'amylose', and 'amylopectin', all terms connected with starch and its chemistry.
Related word forms
How amyloid is actually used
Almost exclusively used in scientific, medical, and technical contexts; rarely encountered in everyday conversation. In contemporary usage it overwhelmingly refers to the pathological protein deposits rather than its original chemical sense.
Easily confused with amyloid
Amylase is a digestive enzyme that breaks down starch, whereas amyloid is a pathological protein deposit or a starch-like substance.