How is the term 'man-hours' best defined?

The term 'man-hours' is best defined as the total labor hours contributed by workers. This metric is often used in various industries to assess the human effort needed to complete a task or project, integrating both the number of workers involved and the time they dedicate to the work. By quantifying work in man-hours, organizations can better plan resources, schedule projects, and evaluate productivity.

In contrast, the other options focus on specific aspects of work but do not encapsulate the broader meaning of 'man-hours.' For instance, time allocated for machine operation relates primarily to equipment usage rather than human labor. Similarly, time spent in training sessions pertains only to the educational aspect and not the actual productive labor. Lastly, hours lost due to inefficiencies concern the negative impact on productivity rather than a measure of actual work performed. Thus, 'man-hours' is specifically about the labor provided by individuals, making the selected definition the most accurate.