Which of the following terms is synonymous with 'testes' in medical terminology?

In medical terminology, the correct term synonymous with 'testes' is 'orchid/o'. This root word specifically refers to the testes, which are the male gonads responsible for producing sperm and hormones such as testosterone. The term 'orchid' actually stems from the Greek word for testicle, illustrating its direct association with male reproductive organs.

The other terms provided have different meanings related to other body parts or functions: 'onc/o' refers to tumors or cancer, often used in conjunction with terms that describe types of cancer; 'oophor/o' is the term for ovaries, which are the female reproductive organs responsible for producing eggs; and 'opt/o' pertains to the eye or vision. Understanding these distinctions highlights the specificity of medical terminology, where each prefix or root word is distinctly linked to particular anatomical structures or medical concepts.