Scalability is the capability of a system to handle a growing amount of work or its potential to accommodate growth. A scalable system can increase its performance and capacity by adding resources, such as additional hardware or nodes, without requiring significant changes to the underlying architecture. Scalability is a critical attribute for applications and systems that need to handle increasing workloads, user demand, or data volumes over time. It ensures that a system can maintain performance and reliability as it expands, making it a key consideration in designing and implementing modern software solutions.