Here's why:

* No cells: Living things are made up of cells, the basic building blocks of life. Rocks are made of minerals and don't have cells.

* No metabolism: Living things have a metabolism, a set of chemical reactions that allow them to grow, reproduce, and maintain themselves. Rocks don't have a metabolism.

* No growth or reproduction: Living things grow and reproduce. Rocks don't grow or reproduce in the way living things do.

* No response to stimuli: Living things respond to changes in their environment. Rocks don't respond to stimuli.

While some rocks may look like they're moving (like a glacier) or growing (like stalactites and stalagmites), these processes are caused by external forces and not by any inherent life within the rock itself.