Define osmosis.

Osmosis is the net movement of free water molecules from an area of higher water potential to an area of lower water potential through a partially permeable membrane.
Water potential = a measure of the number of free water molecules there are in a solution.Partially permeable membrane = a membrane with tiny holes in it that allows tiny molecules such as water to pass through"Net" because the water molecules move in both both directions, but move in one direction more than the other."Free" because only the water molecules that are not attached to any solutes in the solution can pass through the membrane."Higher" and lower", not just "high" and low", because the water potential can be low in one solution but even lower in the other solution and osmosis will still occur.