Which option correctly defines the prefix endo-?

Which option correctly defines the prefix endo-?

• A. Over
• B. Across
• C. Within
• D. Surrounding

Answer: (C)

Endo- signals inside or within a structure. When this prefix is attached to a root, it describes something located inside or occurring within. Examples show how this works: endoscope is an instrument used to look inside the body, endocardium is the inner lining of the heart, endometrium is the inner lining of the uterus, and endotherm refers to animals that maintain internal heat. This contrasts with prefixes that mean outside or around, like exo- (outside) or peri- (around). Therefore, the meaning that fits endo- is “within.”

Endo- signals inside or within a structure. When this prefix is attached to a root, it describes something located inside or occurring within. Examples show how this works: endoscope is an instrument used to look inside the body, endocardium is the inner lining of the heart, endometrium is the inner lining of the uterus, and endotherm refers to animals that maintain internal heat. This contrasts with prefixes that mean outside or around, like exo- (outside) or peri- (around). Therefore, the meaning that fits endo- is “within.”