The term "humidity indicator" can be substituted with a variety of words and phrases. For instance, one may use the term "hygrometer" to indicate a device that measures humidity levels. "Moisture meter" is another phrase that can be used to describe a tool that indicates the amount of water vapor in the air. Additionally, "humidity sensor" may be a suitable synonym for a device that detects or measures humidity. "Humidity gauge" is yet another term that can be used to refer to a tool that displays the amount of moisture in the air. All of these synonyms effectively convey the idea of a device or tool that measures humidity levels.