Final answer:
The right hemisphere taking over language functions from a damaged left hemisphere exemplifies the brain's plasticity, which is its ability to adapt and change in the face of injury or experience.
Step-by-step explanation:
If a slow-growing left-hemisphere tumor disrupts language, the right hemisphere taking over this language functioning best illustrates plasticity. The term plasticity refers to the brain's ability to change and adapt as a result of experience. In the case of a split-brain patient, where the corpus callosum is cut to treat severe epilepsy, the two hemispheres become isolated. This medical procedure reveals the specialized functions of each hemisphere. Typically, the left hemisphere is associated with language functions, and so separation often impairs verbal abilities associated with the right side of sensory input. However, damage to the right hemisphere can also affect the use of language, understanding of nonliteral speech, and the emotional aspects of speech.