Question

What is actually osmosis? Define it.

Answer 1

Movement of water through a semi-permeable membrane from high water concentration to low water concentration is called osmosis. Osmosis is a type of diffusion. Cell membrane is a semi-permeable membrane. Substances move across the cell membrane because of osmosis. Seeds swell up; when soaked in water; because of osmosis.

Actually osmosis occurs to equalize the solute concentrations on the two sides of the semi-permeable membrane.

By definition, we can explain osmosis as:
Osmosis is the spontaneous net movement of solvent molecules through a semi-permeable membrane into a region of higher solute concentration, in the direction that tends to equalize the solute concentrations on the two sides.