This document discusses risk and uncertainty in construction projects. It defines uncertainty as a lack of certainty involving variability and ambiguity, while risk can be quantified using probability distributions. Sources of uncertainty include unclear communication, unestimated work amounts, lack of management tools, and unclear responsibilities. The top 10 risks related to project objectives are listed as cost overruns, delays, quality issues, environmental impacts, and safety concerns. Risk management for construction projects involves planning, identification, analysis, response, and monitoring of risks over nine areas including scope, schedule, costs, quality, and communications. Managing both internal and external project risks is important for project success.