The combining form meaning cancer or tumor is which?

• A. oo
• B. onc(o)
• C. odon
• D. ophthal

Answer: (B)

The main idea here is how medical terms are built from combining forms that carry specific meanings. The form onc/o means cancer or tumor. It comes from the Greek onkos, meaning mass or swelling, and it appears in terms like oncology (the study of cancer), oncologist (a doctor who treats cancer), and oncogenic (having the potential to cause cancer). The other forms don’t convey cancer or tumor: oo relates to egg or ovum, odon means tooth, and ophthalm- relates to the eye. So onc/o is the right forming element for cancer or tumor.