What does chemotherapy mean?
Chemotherapy is the medical treatment of disease using chemical substances, though in modern usage the word refers almost exclusively to the treatment of cancer with drugs that destroy or inhibit the growth of malignant cells. These cytotoxic medications are usually given intravenously or as tablets over a series of cycles, and because they act on all rapidly dividing cells rather than targeting cancer alone, they often cause side effects such as fatigue, nausea, hair loss, and lowered immunity. The word derives from the German chemotherapie, coined in the early twentieth century from Greek roots meaning 'chemistry' and 'treatment.' Chemotherapy may be used alone or alongside surgery and radiotherapy, either to cure disease, shrink tumours before other treatments, or relieve symptoms in advanced illness. Colloquially shortened to 'chemo,' the term is widely understood but emotionally charged, reflecting both the hardship and the hope associated with modern cancer care.
nounThe treatment of disease, especially cancer, using chemical substances that kill or slow the growth of diseased cells. It typically involves administering cytotoxic drugs that target rapidly dividing cells throughout the body.
- The use of cytotoxic drugs to treat cancer by killing or slowing the growth of cancerous cells.
- More broadly, the treatment of any disease using chemical agents.
"After her surgery, she underwent six months of chemotherapy to reduce the risk of the cancer returning."
"He began chemotherapy within weeks of the diagnosis, receiving infusions every three weeks."
"Antibiotics are a form of chemotherapy in the broadest sense — chemicals deployed against disease-causing organisms."
Rarely pluralised; the uncountable singular is standard even when multiple courses or types of treatment are meant. A plural form exists in technical writing when distinguishing distinct therapeutic approaches, but ordinary usage avoids it.
"Modern oncology draws on a range of different chemotherapies, each targeting cancer cells through distinct mechanisms."
Chemotherapy was born from wartime poison gas — after a WWII bombing of Allied ships carrying mustard gas, doctors noticed the survivors had destroyed bone marrow and wondered if the same agent could kill cancer cells.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of chemotherapy
The word chemotherapy comes from the German Chemotherapie, formed from the Greek-derived element chemo-, relating to chemistry (ultimately from Greek khēmeia, referring to alchemy), combined with therapeia, the Greek word for healing or medical attendance. The concept emerged in the early twentieth century, when scientists such as Paul Ehrlich pioneered the idea of using specific chemical compounds to selectively attack disease-causing organisms. Its application to cancer treatment developed later, expanding dramatically after the Second World War when researchers observed the effects of mustard gas on dividing cells.
Related word forms
How chemotherapy is actually used
In everyday usage, 'chemotherapy' almost always refers to cancer treatment; the broader medical sense (any drug-based treatment of disease) is mostly confined to clinical contexts. The word carries serious emotional weight for many speakers because of its association with cancer, so it is generally used with sensitivity. In casual speech it is often shortened to 'chemo.'
Easily confused with chemotherapy
Radiotherapy treats disease using ionizing radiation rather than chemical drugs.
Immunotherapy harnesses the patient's own immune system to fight disease, whereas chemotherapy uses drugs to directly kill or slow dividing cells.