A hygrograph is a device used to measure the humidity or moisture levels in the air or in a specific environment. Other words that can be used as synonyms for hygrograph include a hygrometer, which measures humidity, and a psychrometer, which measures both temperature and humidity. Other related terms include a dewpoint hygrometer, which measures the temperature at which dew will start to form, as well as a humidity sensor or moisture meter, which are devices used to measure moisture content in various materials. In general, these devices are used in weather forecasting, agriculture, and industrial applications to monitor and control moisture levels in various settings.