"Main" emphasizes that something supplies the most of some kind of stuff. "Leading" emphasizes the rank order in a competition. Thus, you can say that "Japan is the leading nation in life expectancy," because it has a longer life expectancy than any other nation. You cannot say "Japan is the main nation in life expectancy," because life expectancy is not a kind of stuff. Japan does not manufacture life expectancy, does not export life expectancy, does not supply the world with life expectancy. In fact, those phrases are nonsense. You can say "the Quabbin Reservoir is the main source of water for Boston," because it supplies most of Boston's water. You wouldn't say "the Quabbin Reservoir is the leading source of water for Boston," because we don't think of the reservoirs as being in competition with each other. You can say "Volkswagen is the leading auto manufacturer in the world," because it makes more cars than any other company. You wouldn't say "Volkswagen is the main auto manufacturer," because it only has a 12% global market share. It's not the main automaker. There are plenty of others.

The main Source of Nile River Located in Ethiopia which lead to Egypt and flows into the Mediterranean Sea .. the Leading supplier for the water is the HIgh Dam in Aswan :D

Main and leading can be synonyms, but they can also be very different. You could describe the candidate most likely to win an election as the main or leading candidate. These would be more-or-less synonymous. I do say 'more-or-less' ! However, in the following sentences 'main' CANNOT be changed to 'leading'. Simply doesn't work! "The main season for strawberries is the early summer." "The main source of energy is oil." "The main living area in the house was the lounge-cum-diner." Try this example and see if you can see the difference. "The main source of energy is oil. The leading supplier is the Mega-Oil Company."

Omg Jerry! haha.. yes yes you are right...

Correction: "Do these two words have the same meaning?"