I believe "shortfall" relates to a failure according to some plan or forecast. A shortage is just a paucity or lack.

If there is a shortage, it means you don't have what it takes to meet a need. e.g. People are dying due to the water shortage. If there is a shortfall, it means there is less of something than you expect. e.g. The country is expecting a shortfall of over 100 homes over the next two years.

Hi Serg, They both have the same meaning to describe something that you have less of what you truly want. However, I would say that "shortage" is more commonly used in writting and talking compared to "shortfall". -Phuc