Heart (noun)

1. A hollow muscular organ that pumps blood through the circulatory system by rhythmic contraction and dilation.
2. The center of something.

Origin:

Middle english herte, from old english heorte; akin to old high german herza heart.

Examples:

1. She felt a pang in her heart.
2. He has a weak heart.
3. Her heart was pounding with excitement.
4. He put his heart and soul into the project.
5. The heart of the city is bustling with people.
6. She's the heart and soul of the team.