Final answer:
Metamorphism is the process of changing a pre-existing rock's physical and/or chemical structure through changes in temperature, pressure, or interaction with fluids, resulting in a new metamorphic rock.
Step-by-step explanation:
The feature of the rock cycle where rocks undergo change without melting or becoming sediments is called metamorphism. This process involves the alteration of a pre-existing rock (protolith) due to changes in temperature, pressure, or by contact with chemically reactive fluids. The recrystallization that occurs during metamorphism causes the minerals in the rock to change in size, shape, and/or composition, resulting in a new metamorphic rock with different properties from the original. Metamorphic rocks may exhibit foliation, which is a kind of layering or banding as a result of reorientation of the rock's minerals.
Other processes in the rock cycle include the formation of igneous rocks from cooled magma or lava and the creation of sedimentary rocks from weathered rock particles that are cemented together. Each rock type can be transformed into another through various processes, such as melting, weathering, lithification (compaction and cementation of sediments), and metamorphism, completing the dynamic and continuous nature of the rock cycle.