* Hemisphere: This is the most common answer. A hemisphere is literally half of the Earth's sphere. We usually talk about the Northern Hemisphere and Southern Hemisphere, divided by the equator.
* Landmass: The landmass of Earth is called the continents. About 29% of Earth's surface is land, while the remaining 71% is water.
* Ocean: About 71% of Earth's surface is covered in water, which makes up the oceans.
So, it really depends on what kind of "half" you're asking about!
