1. In literature and film:
* An antagonist is a character who actively opposes or works against the protagonist, the main character. They are often the source of conflict and tension in the story.
Examples:
* Voldemort in the Harry Potter series
* Darth Vader in Star Wars
* The Joker in Batman
2. In biology and medicine:
* An antagonist is a substance that blocks or reduces the effect of another substance, often a neurotransmitter or hormone.
Examples:
* Beta-blockers are antagonists that block the effects of adrenaline and noradrenaline.
* Naloxone is an antagonist that blocks the effects of opioids.
Important Note:
It's important to be aware of the context when encountering the word "antagonist" to understand its intended meaning.