cancer
Americannoun
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Pathology.
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a malignant and invasive growth or tumor, especially one originating in epithelium, tending to recur after excision and to metastasize to other sites.
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any disease characterized by such growths.
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any evil condition or thing that spreads destructively; blight.
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(initial capital letter) the Crab, a zodiacal constellation between Gemini and Leo.
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Astrology. Cancer,
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the fourth sign of the zodiac: the cardinal water sign.
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a person born under this sign, usually between June 21 and July 22.
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tropic of Cancer. tropic1a
noun
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astronomy a small faint zodiacal constellation in the N hemisphere, lying between Gemini and Leo on the ecliptic and containing the star cluster Praesepe
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astrology
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Also called: the Crab. the fourth sign of the zodiac, symbol ♋, having a cardinal water classification and ruled by the moon. The sun is in this sign between about June 21 and July 22
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Also called: Moonchild. a person born during a period when the sun is in this sign
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See tropic
adjective
noun
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any type of malignant growth or tumour, caused by abnormal and uncontrolled cell division: it may spread through the lymphatic system or blood stream to other parts of the body
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the condition resulting from this
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an evil influence that spreads dangerously
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A disease characterized by any of various malignant neoplasms composed of abnormal cells that tend to proliferate rapidly and invade surrounding tissue. Without treatment such as chemotherapy or radiation, cancer cells can metastasize to other body sites and cause organ failure and death.
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A malignant tumor.
Usage
What does Cancer mean? Cancer is the name of a constellation that’s interpreted as resembling a crab. It’s sometimes referred to as The Crab. A constellation is a group of stars that appear near each other in the sky—especially a group that has been given a name. Cancer is considered one of the 12 zodiacal constellations—constellations that appear within a particular portion of the sky called the zodiac. In astronomy, the zodiac is the band of sky along which the paths of the sun, the moon, and the planets appear to move. Despite its basis in astronomy, the word zodiac is mainly associated with and most often used in the context of astrology, the nonscientific practice in which the positions of heavenly bodies at certain times are thought to influence or be correlated with human behavior and events. In astrology, zodiac refers to a diagram (often a circular one) representing the zodiac belt and showing the symbols associated with each of the 12 constellations or sections, which are called the signs of the zodiac. Cancer is one of these signs. It is situated between Gemini and Leo and is considered the fourth sign of the zodiac. The other signs of the zodiac are Aries, Taurus, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, and Pisces. The position of the sun in a particular portion of the zodiac at the moment of a person’s birth is thought to correlate with their personality. This is what people are referring to when they talk about their zodiac sign (or star sign or often just sign). People whose sign is Cancer are those born between June 21 and July 22. In the context of the zodiac, the word Cancer can also be used as a noun to refer to someone who is born during this time, as in I was born in early July, so I’m a Cancer. The word Cancerian can be used to mean the same thing. It can also be used as an adjective form of Cancer. Example: I’m a Cancer, but I don’t think I fit into the sensitive Cancer stereotype.
Closer Look
The human immune system often fights off stray cancer cells just as it does bacteria and viruses. However, when cancer cells establish themselves in the body with their own blood supply and begin replicating out of control, cancer becomes a threatening neoplasm, or tumor. It takes a minimum of one billion cancer cells for a neoplasm to be detectable by conventional radiology and physical examinations. Cancer, which represents more than 100 separate diseases, destroys tissues and organs through invasive growth in a particular part of the body and by metastasizing to distant tissues and organs through the bloodstream or lymph system. Heredity, lifestyle habits (such as smoking), and a person's exposure to certain viruses, toxic chemicals, and excessive radiation can trigger genetic changes that affect cell growth. The altered genes, or oncogenes, direct cells to multiply abnormally, thereby taking on the aggressive and destructive characteristics of cancer. Treatments such as surgery, chemotherapy, and radiation are effective with many cancers, but they also end up killing healthy cells. Gene therapy attempts to correct the faulty DNA that causes the uncontrolled growth of cancer cells. Researchers are investigating other treatments, such as immunotherapy (the stimulation of the body's natural defenses), vectorization (aiming chemicals specifically at cancer cells), and nanotechnology (targeting cancer cells with minute objects the size of atoms).
Discover More
The term cancer is often used to describe a nonmedical condition that is undesirable, destructive, and invasive: “Watergate was a cancer on the presidency.”
Other Word Forms
Etymology
Origin of cancer
First recorded in 1350–1400; Middle English, from Latin: literally, “crab”; Latin stem cancr-, dissimilated from unattested carcr-, akin to Greek karkínos, Sanskrit karkata “crab”; see canker
Explanation
Cancer is a disease in which cells grow uncontrollably and form tumors. The best chance of surviving cancer usually involves finding and treating it early. The word cancer actually means "crab," like the zodiac sign. Around 400 B.C., Greek physician Hippocrates is said to have named the disease karkinos, which is Greek for "crab," when he noticed that tumors formed a crab-like shape. The word cancer describes not just a disease, but any sort of evilness that can spread. Hatred and bigotry are cancers that can destroy communities.
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
See Examples For:
When Zambada was 12, his father died of brain cancer.
From Los Angeles Times ● Jul. 20, 2026
Keegan revealed he had stage four cancer in June, which is the most advanced stage of cancer and means the disease has spread to other parts of the body.
From BBC ● Jul. 20, 2026
"If improving how sunscreen looks leads to more consistent use, it could have real implications for skin cancer prevention."
From Science Daily ● Jul. 20, 2026
Stourton, who had been diagnosed with prostate cancer in 2014, died on Saturday surrounded by his family, the BBC announced in a statement.
From BBC ● Jul. 20, 2026
How would they know that their great-grandpa died of cancer?
From "Everything Sad Is Untrue" by Daniel Nayeri
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Her doctor at Cedars-Sinai knew an oncologist at the MD Anderson Cancer Center in Houston, a leader in treating anaplastic cancer.
From Los Angeles Times ● Jul. 18, 2026
To better understand why, researchers launched the Epidemiology of Young Lung Cancer Project.
From Science Daily ● Jul. 13, 2026
That work led to a 2000 article in the Journal of the National Cancer Institute demonstrating that HPV-related cases were very different from those related to tobacco or alcohol—and less deadly.
From The Wall Street Journal ● Jul. 10, 2026
Cancer is not the death sentence it used to be, but the sooner you catch it, the better the outcome.
From Los Angeles Times ● Jul. 7, 2026
It was made out to the American Cancer Society in the amount of five hundred dollars.
From "Schooled" by Gordon Korman
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The so-called super Earth — known as 55 Cancri e — is among the few rocky planets outside our solar system with a significant atmosphere, wrapped a blanket of carbon dioxide and carbon monoxide.
From Seattle Times ● May 8, 2024
One of the most well-known of these mysterious burning worlds is 55 Cancri e, an exoplanet about 41 light-years away that scientists describe as home to both sparkling skies and roiling lava seas.
From Science Daily ● Sep. 27, 2023
Scientists hope to learn whether 55 Cancri e even has an atmosphere, and if so what is it made of.
From Salon ● Sep. 15, 2022
The star, however, is smaller and cooler than that of 55 Cancri e.
From Scientific American ● Jun. 3, 2022
Three stars in close proximity, and found to be in physical connection, as, for instance, ζ Cancri.
From The Sailor's Word-Book An Alphabetical Digest of Nautical Terms, including Some More Especially Military and Scientific, but Useful to Seamen; as well as Archaisms of Early Voyagers, etc. by Belcher, Edward, Sir
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.