Diffusion: The net movement of particles from an area of higher concentration to an area of lower concentration.

Here are three ways substances can move in and out of the cell:

1. Diffusion: The net movement of particles from an area of higher concentration to an area of lower concentration.
2. Osmosis: The net movement of water molecules across a partially permeable membrane from a region of higher water potential to a region of lower water potential.
3. Active Transport: The movement of molecules across a cell membrane against their concentration gradient, requiring energy (ATP).