Here's why:

* Compound: A compound is formed when two or more different elements are chemically bonded together in a fixed ratio. In this case, H₂O (water) is a compound made of hydrogen (H) and oxygen (O).

* Coefficient: The number "3" in front of H₂O is a coefficient. It indicates that there are three *molecules* of water.

So, while there are three molecules of the compound, there's still only one type of compound present: water (H₂O).