how man speices of dolphin in the world?

Answer 1

There is 40 species of dolphins.

Edit: Although there are 26 species of oceanic dolphin properly Delphinidae, that does not count all the river dolphins and other cetaceans in the same grouping as them.

Edit#2: This book Guide to Marine Mammals of the World by National Audubon Society says there are 33 ocean dolphins and 4 river dolphins for a total of 37. This book however is around 5 years old.

Answer 2

well, there are 32 different dolphin species. There are also two closely related families - the white whales (Monodontidae) and river dolphins (Platanistidae).
well, you can visit the website below for more info :)

Answer 3

67 in the group Odontoceti (toothed whales)
about 40 of which are dolphins