Chemical reagent refers to a substance that is used to bring about a chemical reaction, either by itself or in combination with another substance. There are several synonyms for the term chemical reagent, including reactant, agent, indicator, and catalyst. A reactant is a substance that is consumed in a chemical reaction, while an agent is a substance that produces a particular effect or result. An indicator is a substance that changes color or some other characteristic when it comes in contact with another substance, while a catalyst is a substance that speeds up a chemical reaction without being consumed in the process. Regardless of the synonym used, chemical reagents play an essential role in chemical reactions and scientific research.