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A useful five-part classification is electrostatic double-layer, dispersion, steric, depletion force and solvent-mediated interactions. It is a practical classification rather than a unique exhaustive list.

Electrostatic double-layer forces arise from surface charge and mobile-ion redistribution. Like-charged surfaces often repel; opposite charges can attract. Their range changes with salt screening. London dispersion forces comes from correlated electronic fluctuations and is one contribution to Van der Waals force; its sign and strength across a medium depend on dielectric response.

steric stabilization occurs when adsorbed or grafted layers overlap, increasing chain confinement and/or local osmotic free energy. depletion force arises when smaller nonadsorbing solutes are excluded from a narrow gap: their greater accessible volume outside favors bringing the large particles together. Structured-solvent forces include short-range hydration force and hydrophobic attraction; their microscopic origin differs from the depletion force of an added solute.

The original sketches show double-layer overlap, a polymer-coated gap, depletion force exclusion and solvent structure, alongside a dispersion-potential curve. A realistic suspension can experience several simultaneously. Charge neutrality of a particle does not remove dispersion, steric or solvent-mediated interactions.

DLVO theory adds attractive Van der Waals forces and electric double layer repulsion to obtain an effective colloid pair potential. For two identical spheres of radius $b$ at a surface gap $h\ll b$, a useful schematic form isHere $A_H$ is the Hamaker constant. For a symmetric monovalent electrolyte with number density $n$ of each ionic species, ${\kappa }_D^2=2n{e}^2/(ϵk_{B}T)$. The exponential is a simplified screened repulsion; its amplitude depends on electric potential at the surface, charge regulation and geometry. Constant-charge and constant-potential boundary conditions need not produce the same close-approach law.

A primary attractive minimum near contact may be separated from dispersed configurations by an energy barrier; a shallower secondary minimum can produce loose reversible aggregation. A barrier much larger than $k_{B}T$ can give long-lived kinetic stabilization without making the dispersed state the global free-energy minimum. Adding salt shortens the Debye–Hückel screening length and can lower the barrier, allowing colloidal coagulation. Changing pH can alter surface ionization, so screening alone does not determine stability.

One can vary salt concentration while holding particle concentration, temperature and pH fixed, then follow particle aggregation using light scattering or microscopy. A solvent-only control and an independently measured surface-charge indicator help distinguish a change of screening from adsorption or charge reversal. Classical DLVO theory omits steric stabilization, hydration forces and strong ionic correlations; the formal attraction diverging at contact is cut off by molecular-scale physics.