Particles in agglomerates are linked by stronger interactions than in aggregates. Agglomerates can be considered as "secondary" particles having an inner surface, i.e. in many cases, their internal surface area is much higher than the external surface area. Yet agglomerates can have a structured porous system. Examples of agglomerates are sandstone, silica gel, etc.

There is no clear boundary between the terms "aggregate" and "agglomerate" and sometimes they are used to describe similar objects. In some cases (for example, to describe the technology of pigments, etc.) the terms "aggregate" and "agglomerate" are used with meanings contradicting with the recommendations of the International Union of Pure and Applied Chemistry (IUPAC). Therefore the terms "aggregate" or "agglomerate" are often accompanied by a description (strong or weak) of the interactions between the primary particles.