 Let's explore what osmosis is. For that, let's take an example. Imagine we have a container where we have some water and on one side we're gonna sprinkle some salt. Now, of course, the salt would completely, you know, distribute itself throughout the water. But what if we keep some kind of a membrane in between that does not allow the salt to pass from here to here? Okay, so imagine that there are tiny holes in that membrane which are too small for salt molecules to pass through. So they can't pass through, okay? Then these salt molecules are stuck over here. They can't go from here to here. But let's say that the holes are big enough for water molecules to move across. Then we will call such a membrane a semipermeable membrane. So what's a semipermeable membrane? Well, it's a kind of membrane that allows the solvent molecules to go through. So in this particular case, the solvent is the water. You can't see the water molecules because I've not drawn the water molecules over here. So it allows the solvent molecules to go through, but it does not allow the solute molecules to go through. So the solute molecules like salt, it doesn't allow it to go through it, okay? So that's what a semipermeable membrane is. So now the question is, what's going to happen? Well, first of all, you probably already know that because the concentration of solute over here is high and you hardly have no concentration over here. You have nothing over here. The solute particles, the salt would want to go from here to here. That's called diffusion. They want to diffuse from higher concentration to lower concentration. They want to do that. But because you have a semipermeable membrane, they are not unable to do it, they can't go from here to here. So what's going to happen? Well, since the solute molecules can't go from here to here, you know what's going to happen? The solvent molecules will start moving from here to here. Can you see what's going on? So nature wants to somehow make sure the concentration equalizes, right? But since the solute molecules can't go from here to here, the only way to try to equalize the concentration is for the water to go from here to here. So this movement of water that's happening from the lower solute concentration to the higher solute concentration is what we call osmosis. And so what is the definition of osmosis? Now we can understand the definition of osmosis. Osmosis is the movement of solvent molecules. You can see solvent water from a region of lower solute concentration. See, this was the lower solute concentration to a region of higher solute concentration. But when does this happen? This happens through a semipermeable membrane, when there is a semipermeable membrane. If there was no semipermeable membrane, water wouldn't have to do it, the salt would have just diffused. Osmosis plays an important role in cells and living beings and all of that and we'll explore that in a future video.