What is the difference between reagents and reactants?
They are substances that cause a chemical reaction. They may or may not be consumed in a chemical reaction, whereas reactants will be.
Hence, solvents could be considered reagents, despite how they are generally not consumed in the reaction. Catalysts can be considered reagents, but not reactants. Substances that are used to test whether a reaction has occurred (such as pH indicators, e.g. phenolphthalein, methyl orange, bromothymol blue, etc) are also reagents.