What is the approximate size of a normal heart?

The approximate size of a normal heart is about the size of your fist. This comparison is often used because it helps convey not only the size but also the compact nature of the heart as it fits comfortably within the chest cavity. The heart is a muscular organ responsible for pumping blood throughout the body, and its size is proportional to the overall body size of an individual. Generally, the heart's size can vary slightly between individuals, but the fist analogy is a good, relatable measure for most adults.

Other options, while they may suggest sizes that are relatively familiar, do not accurately represent the typical size of the heart. A grapefruit or a tennis ball would imply a heart that is uncommonly large, while a walnut is too small to reflect the true dimensions of an adult heart. Thus, the comparison to a fist is the most accurate and informative for understanding the heart's size.