Inhibitor (noun)

1. A substance or factor that slows down or stops a reaction or process.
2. Something that restrains or slows down the action of a person or organism.

Origin:

Mid 17th century: from latin inhibere "to hold back" + -tor.

Examples:

1. The new drug was designed to act as an inhibitor of the virus.
2. The cold weather was a major inhibitor of plant growth.
3. Her shyness was a major inhibitor in her social life.
4. The lack of resources became an inhibitor for the company's growth.
5. His anger was a major inhibitor of his decision-making ability.