Here's why:

* Solid: While the lower mantle experiences immense pressure and heat, it's still considered solid. The minerals within it are under such immense pressure that they cannot melt, even though they are extremely hot. They behave in a way that is more like a very viscous fluid, able to flow incredibly slowly over geological time.

* Hot: The lower mantle is extremely hot, with temperatures ranging from 1,900 to 3,700 degrees Celsius (3,450 to 6,700 degrees Fahrenheit).

* Dense: The lower mantle is incredibly dense due to the immense pressure from the weight of the Earth above it.

So, while it's true that the lower mantle has characteristics of a solid and a fluid, the term "solid" most accurately reflects its state of matter.