How many winds are there in Mahjong?

The four directions or 'winds' (east, north, west, south) - four copies of each (16 tiles)

http://www.pagat.com/rummy/mahjong.html

Wind Tiles -- Each game contains a set of tiles inscribed with the Chinese characters for the four compass directions, representing the four winds: EAST / SOUTH / WEST / NORTH
The four winds are:
East (dong)
South (nan)
West (xi)
North (bei)
There are four of each of these tiles in the game.