An "organ" is a specialized structure within a living organism that performs a specific function essential for survival. In humans and many animals, organs are part of larger systems, such as the digestive system or respiratory system. Examples of organs include the heart, which pumps blood, and the lungs, which facilitate breathing. In plants, organs also play crucial roles. The main organs include roots, which anchor the plant and absorb water and nutrients, stems, which support the plant and transport substances, and leaves, which are responsible for photosynthesis. Each organ works together to ensure the overall health and growth of the organism.