Which of the following root words indicates "tumor"?

The root word that indicates "tumor" is found in the first choice. The suffix "-oma" is commonly used in medical terminology to denote the presence of a tumor or mass. For example, terms like "carcinoma" refer to a cancerous tumor, while "lipoma" refers to a benign tumor made of fat tissue.

The prefix "onco-" is also related to tumors, specifically in a broader context of oncology, which is the study and treatment of tumors. Therefore, the combination of "-oma" and "onco-" effectively encapsulates the concept of neoplasms or tumors.

The other options do not relate to tumors. The suffix "-otomy" refers to a surgical incision, "osteo-" pertains to bones, and "-osis" indicates a condition, often a disease or abnormal state. Understanding these distinctions is crucial in medical terminology, as they directly relate to the diagnosis and treatment of various health conditions.