Final answer:
A mega-project is an extensive and costly venture, often exceeding $1 billion, affecting millions of people, and spans several years. Examples include infrastructure projects like bridges, tunnels, and airports.
Step-by-step explanation:
A mega-project is a very large project that typically costs over $1 billion, affects over one million people, and lasts for several years. These immense ventures are characterized by substantial financial investments, profound complexity, and long-lasting impact. Examples of mega-projects include the construction of major bridges, tunnels, high-speed rail lines, airports, seaports, and large-scale urban redevelopment endeavors.
A megaproject is an extremely large-scale investment project. According to the Oxford Handbook of Megaproject Management, "Megaprojects are large-scale, complex ventures that typically cost $1 billion or more, take many years to develop and build, involve multiple public and private stakeholders, are transformational, and impact millions of people".
However, $1 billion is not a constraint in defining megaprojects; in some contexts a relative approach is needed, such as in developing countries, where a much smaller project (such as one with a $100 million budget) could constitute a megaproject. Therefore, a more general definition is "Megaprojects are temporary endeavours (i.e. projects) characterised by: large investment commitment, vast complexity (especially in organisational terms), and long-lasting impact on the economy, the environment, and society".