In the medical world, proper use of words is highly called for because a simple mistake could complicate things usually unwanted for the patients. Because this field has full of jargons that most are too technical to not easily be sifted and digested by the general public, putting them in a layman’s term is indeed helpful.
A good example of which are the words “side effect” and “main effect”. These, are more often than not, interchanged or used instead of the other. Doing so is not just wrong but also dangerous to the people’s health.
A side effect of any substance pertains to the result beyond the main or primary action that is intended by the physician giving drug prescription. The doctor, likewise, foresees this extra consequence.