The word cancer came form a greek word cancrum . the meaning of this word is crab. It is dreaded disease characterized by uncontrolled growth of cells . the results is the formation of tumour. A tumour is a mass of tissue formed by the abnormal proliferation of cells .tumours may or may not be cancerous . the study about the cancer is known as oncology. Turmours are of two types . they name as benign tumour and malignant turmour. The tumour which is confined to the place of it s origin is known as benign tumour .these tumours are not migrate from one place to another. The malignat tumours are very serious. These tumours are carried by blood and lumph to other body parts , where they multiply to produce secondary growth .these tumours are also known by name cancerous tumours. The spreading of cancerous cells to different body parts is known as metastasis. The agents which cause cancer are called by name carcinogens. One of the important carcinogen is uv rays .. cigerrete smoking , coal tar , carbonmonoxide etc can act as carcinogens. Symptoms are change in bowel or bladder, a sore which does not heal, severe bleeding , indigestion, difficulty in swallowing etc. cancer can be cured by radiation therapy in its starting stage, in sever case no treatment is available.