What term describes a group of organs working together?

The term that describes a group of organs working together is "organ system." An organ system is made up of multiple organs that collaborate to perform a specific function necessary for the organism's survival. For instance, the digestive system includes various organs like the stomach, intestines, and liver, all of which work together to break down food and absorb nutrients.

In contrast, "tissue" refers to a group of similar cells that work together to perform a particular function, while an "organ" is a single structure composed of different tissues that carry out a specific task. "Biological system" is a broader term that might refer to various systems and processes across different levels of biological organization but does not specifically indicate a focused collaboration of organs like an organ system does. Therefore, "organ system" is the most accurate term for a group of organs functioning together.