Water has always been the major uncertainty at Yucca Mountain.

Another major uncertainty is whether the Republicans, after such a bitter fight, can pull their party together.

"The members recognized that the outlook for the economy was subject to major uncertainties," said the official summary of the meeting.

A major uncertainty in the model is the unknown activity of the petroleum industry in the future.

Unknown reaction of rivals to the set price is a major uncertainty.

The size of that component remains, perhaps, the major uncertainty in gauging how urgent the climate change problem is.

The flow of water in the area is a major uncertainty.

However, there are always major uncertainties in these studies.

A customary format would be for the affiliate to describe its major uncertainties.

Another major uncertainty is the amount of spending that will be required each period to provide a given standard of living.