antagonist
This term carries a strong sense of friction and opposition. In storytelling, it describes the force that creates conflict, though the antagonist is not always a villain; they are simply the entity that stands in the way of the protagonist's goal.
In a biological or medical sense, the word shifts from a social conflict to a mechanical or chemical one. It describes a substance or muscle that blocks or reverses the effect of another, creating a balance of opposing forces.
Used to count specific individuals or substances that provide opposition, such as multiple antagonists in a complex novel or various chemical antagonists in a lab.
Meanings
Examples
The hero finally confronted his antagonist in the final chapter.
The triceps muscle serves as the antagonist to the biceps.