Which structure is the largest part of the brain?

The cerebrum is indeed the largest part of the brain, making up approximately 85% of its total mass. It is divided into two hemispheres, the left and right, and is responsible for higher brain functions such as thought, learning, memory, emotions, and voluntary muscle movements. The surface of the cerebrum is covered with a layer of neurons known as the cerebral cortex, which is folded into gyri and sulci to increase its surface area.

In contrast, the cerebellum, while also significant in function — particularly in coordinating voluntary movements and maintaining posture and balance — is smaller than the cerebrum. The hypothalamus plays a crucial role in hormone regulation and maintaining homeostasis but is much smaller in size compared to the cerebrum. The pituitary gland, often referred to as the "master gland" of the endocrine system, is even smaller and is primarily involved in hormone release and regulation. Thus, in terms of size and mass, the cerebrum is unequivocally the largest structure in the brain.