Define:

(i) Hypertonic solution;

(ii) Hypotonic solution;

(iii) Isotonic solution.

Part (i): Hypertonic solution:

1. If the surrounding solution has a higher solute concentration compared to inside the cell, then it is called a hypertonic solution.
   
2. Or if the surrounding solution has low solvent concentration compared to the inside of the cell, then it is hypertonic solution.
3. In this condition the solvent moves from the cell to the outside.
   

Part (ii): Hypotonic solution:

1. If the solution in the surrounding has a lower solute concentration as compared to the solute concentration inside the cell, then the solution is called hypotonic.
   
2. Or, if the surrounding solution has high solvent concentration compared to the inside of the cell, then it is hypotonic solution.
3. The solvent moves from the surrounding towards the cells.
   

Part (iii): Isotonic solution:

1. Isotonic solution is the solution that has the same concentration of solute in both surrounding solution and solution inside the cell.
   
2. Or, isotonic solution is the solution that has the same concentration of solvent in both surrounding solution and solution inside the cell.
3. There is no movement of solvent as there is an equilibrium between the surrounding solution and inside of the cell.