In the present paper the general equation and algorithm to derive interfacial forces, acting on phases, situated in the bulk, or at the interface of other phases are given. Based on that, interfacial forces are classified into the following six major types: (i) the "curvature induced interfacial force" (due to Laplace), (ii) the "interfacial gradient force", acting on particles in inhomogeneous fluid phases, due to composition-, temperature- and electrical potential gradient (known as Marangoni force, or thermocapillary force), (iii) the "interfacial capillary force", acting on a phase at an interface of two large phases, including the behaviour of solid particles at the liquid/gas, fluid/fluid and solid/solid interfaces (known as the capillary force, and as the Zener pinning force), (iv) the "interfacial meniscus force," acting between two, solid phases, situated at a curved fluid/fluid or solid/solid interface, the curvature being due to the gravitational or electric fields (known also as the lateral capillary force, or electroclipping force), (v) the "liquid bridge induced interfacial force," acting between two, solid particles, due to the liquid bridge of small volume between them, and NO the "interfacial adhesion force," acting between two particles in a homogeneous fluid phase (with the phenomenological Derjaguin- and Hamaker constants, re-visited). (C) 2005 Springer Science + Business Media, Inc.