Question

What is the exact definition of Rock

Answer 1

Hey,

Rock or stone is a natural substance, a solid aggregate of one or more minerals or mineraloids. For example, granite, a common rock, is a combination of the minerals quartz, feldspar and biotite.
The Earth's outer solid layer, the lithosphere, is made of rock. Rock has been used by humankind throughout history. 

Petrology is the study of rocks.

Rock Classification
Rocks are classified by how they are formed. There are three basic groups, igneous sedimentary, and metamorphic.

Hope this helps. You can clarify any further doubts.

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Answer 2

Answer:

Any natural mass of mineral matter that makes up the earth's crust is called a rock.