What is an antonym for lithosphere?

There isn't a single perfect antonym for "lithosphere" because it refers to a specific, well-defined part of the Earth. However, depending on the context, you could use words that convey the opposite idea, such as:

Direct Opposites:

* Hydrosphere: This refers to all the water on Earth, including oceans, lakes, rivers, and groundwater.

* Atmosphere: This refers to the layer of gases surrounding the Earth.

Related but Opposite Concepts:

* Biosphere: This refers to the part of Earth where life exists, which includes both the lithosphere, hydrosphere, and atmosphere. You could use this to emphasize the living aspect of the Earth in contrast to the rocky lithosphere.

* Mantle: This is the layer of Earth beneath the lithosphere, which is made of hot, dense rock.

* Core: The innermost part of the Earth, consisting of a solid inner core and a liquid outer core.

General Opposites:

* Soft: This emphasizes the opposite of the lithosphere's solid, rocky nature.

* Flexible: This emphasizes the opposite of the lithosphere's rigidity and resistance to movement.

Ultimately, the best antonym for "lithosphere" depends on the specific context and the specific aspect of the lithosphere you want to contrast.