How are osmosis and diffusion alike?
They both relate to movement of molecules from one area to another.
Diffusion is defined as the movement of molecules from an area of high concentration to an area of low concentration. This does not require any membrane (unlike osmosis). For example a spray of perfume in a corner of room may spread though in entire room.
While osmosis is defined specifically as the diffusion of water across a semi-permeable membrane. Latter are very thin layers of material that allow small molecules, like water to pass through but do not allow larger molecules to pass through.
They both relate to movement of molecules.