Which term describes a group of similar cells performing a specific function?

The term that accurately describes a group of similar cells performing a specific function is "tissue." In biological terms, tissues are made up of similar cells that work together to carry out particular tasks, contributing to the overall functioning of an organism. Tissues are typically categorized into four main types in animals: epithelial, connective, muscular, and nervous tissue, each serving distinct roles within the body.

In contrast, the other terms refer to larger or different biological structures. An organ is a structure made up of different types of tissues that work together to perform complex functions. A system consists of multiple organs that work collectively to achieve broad physiological objectives, such as the circulatory system or digestive system. The cellular matrix refers to the extracellular components that provide structural and biochemical support to surrounding cells, but does not define a group of cells working together. Thus, "tissue" is the appropriate term for a collection of similar cells performing a shared function.