Final answer:
In chemistry, indicators are substances that show the presence, absence, or concentration of another substance. They are used to detect certain chemicals or measure the concentration of a substance.
Step-by-step explanation:
In chemistry, the substances that show the presence, absence, or concentration of another substance are called indicators. Indicators are typically used in chemical reactions or experiments to detect the presence of certain chemicals or to measure the concentration of a substance. For example, pH indicators are substances that change color depending on the acidity or alkalinity of a solution.
One example of an indicator is litmus paper, which can be used to test whether a substance is acidic or basic. If the paper turns red, it indicates acidity, while if it turns blue, it indicates basicity. Another example is phenolphthalein, which is a colorless indicator that turns pink in the presence of a base.