Hypotonic = hypoosmotic
Hypoosmotic just refers to the pressure I think. Hypotonic refers to the concentration.
Example
So a 3M cell is placed into a 4M solution.
The cell is hypotonic and hypoosmotic compared to the solution. Water will flow from the cell to the solution.
Hypotonic means there is more water/less solute in whatever you are talking about compared to whatever you are comparing.
So above, the cell is hypotonic. Solution is hypertonic.
If something is hypotonic it is also hypoosmotic.
At least, that's the way I understand it.
