Antonyms and Synonyms

I was teaching my undergraduate students cesarean section. It was a small group, and I began with a question, "Have you seen a cesarean section being performed?" It appeared that each one of the eight had seen one, but on different patients. I asked the next question, “what was the indication for the cesarean section?" The first guy said, ''It was an elective section." This was the first time I had heard this as an indication. ''I don't think you have understood my question," I said. “A cesarean section can be elective or emergency. I want to know what the indication was." One more guy and one girl independently said their indication was 'elective'. I realized had to get through to them somehow. So I said, "Was there any indication or was it unindicated, i.e. without ant indication?" They kept quiet. "See, if one performs a section without any valid reason, it is unindicated. Were the sections you saw being performed indicated or unindicated?" The question was very clear and I expected a clear answer. However they answered “they were elective." I lost my patience then. ''See, there are antonyms and synonyms. Elective and emergency are antonyms. Indicated and unindicated are also antonyms. But elective and indicated are not synonyms." This was the best effort I could make. But they did not show any indication of having understood anything. Finally I said to myself that they were unlikely to remember school level grammar if they could not remember what they had learnt in first year of the medical course. I stopped asking questions and taught them cesarean section in a monologue.