1. all the water on Earth's surface, including oceans, seas, lakes, rivers, ice caps, and groundwater
Usage: used in earth science and environmental contexts; typically treated as a singular, uncountable noun

Examples

• The hydrosphere covers about 71 percent of Earth's surface.
• Scientists study the hydrosphere to understand climate change and water cycles.
• The hydrosphere includes both freshwater and saltwater systems.
• Pollution threatens the health of the entire hydrosphere.
• The hydrosphere interacts with the atmosphere, lithosphere, and biosphere.