What is hypotonic solution?
A hypotonic solution is any solution that has a lower osmotic pressure than another solution. In the biological fields, this generally refers to a solution that has less solute and more water than another solution.
What is a Hypotonic Solution?
Imagine you and two other people are waiting for an elevator in the lobby of a building. When the elevator doors open, you see there are 20 people crammed into that tiny space. Who in their right mind would try and fit on that elevator? Not you! There are just too many people in there. The doors close, and you wait for the next one. This is basically what happens when two solutions meet in biology - the two solutions compare their respective crowdedness to each other, and then each solution reacts accordingly. Sometimes, one solution has more 'stuff' crammed into it than the other. We call this stuff solute. The amount of solute in a solution determines how that solution will react when in the presence of another solution.
A solution can be labeled one of three ways when it is compared to another solution. First, it may be considered an isotonic solution, meaning it has an equal amount of solute and water when compared to another solution. Second, it may be considered a hypertonic solution, meaning it has more solute and less water than another solution. Third, it may be considered a hypotonic solution, meaning it has less solute and more water than another solution. This is the situation described above - when you were waiting in the lobby, you and the two other people were like solute in a solution, and all that space around was the water. When the elevator doors opened, there were a lot more people in a lot less space in that elevator - a lot more solute in a lot less water. Therefore, your lobby was considered hypotonic when compared to the crammed elevator.