Uptime refers to the total time a machine, system, or facility is operational and available for use. It's a critical metric in manufacturing, directly impacting productivity and profitability. 

High uptime means less downtime, fewer production delays, and more output. Conversely, low uptime signals frequent breakdowns, maintenance issues, or operational inefficiencies that can significantly increase costs and disrupt the supply chain. Maximizing uptime is a primary goal for optimizing any manufacturing process.