Metamorphism - it is the chance of minerals or geologic texture in pre-existing of rocks, without the protolith melting into liquid magma.
                        - the change of it occurs primarily due to heat, pressure, and also the introduction of chemically active fluids..... 

I think it is the answer.... But still... I'm not that sure of my answer...
Anyway, I know that i did my best ( it's written in my notebook )....

met·a·mor·phism (mt-môrfzm)
The process by which rocks are altered in composition, texture, or internal structure by extreme heat, pressure, and the introduction of new chemical substances.