Pharmaceutical formulations like suspensions are highly beneficial for delivery of drugs. Several challenges arise during development due to their inherent structural instability. These formulations typically comprise small solid particles (sized between 0.5 and 5 μm) suspended in a liquid or semiliquid that acts as the continuous phase and desired carrier. Theoretical concerns linked to pharmaceutical suspensions (such as interfacial properties, surface free energy, and surface potential along with electric double layer, zeta, and Nernst potential) are conceptualized. Certain other crucial aspects like wetting, electrokinetic phenomena, and DLVO (Derjaguin, Landau, Verwey, and Overbeek) theory with theory of sedimentation are addressed. From a stability point of view, a comprehensive understanding of these factors is crucial since both the characteristics of the carrying liquid and the properties of dispersed solids impact the solidity of the suspension. This chapter delivers an encompassing survey of pharmaceutical suspensions, their introduction, classification, theoretical exploration, assessments, and stability considerations. It is an attempt to equip researchers, practitioners, and stakeholders with a comprehensive understanding of leveraging suspensions for efficient drug delivery.