From Ancient Greek: ὀμοιομερής [homoiomerés], loosely translated: “homogeneous parts”. In the philosophy of Anaxagoras of Clazomenae, an early idea of the concept we would today call “atoms”, i.e. indivisible particles that make up the qualities of a material.
However, Anaxagoras assumed that these smallest particles already contained all the properties of the material they form: In his view, water “atoms” were wet, those of iron hard and those of wool soft.
From a modern perspective – with a better understanding of molecules and material properties – it is not difficult to recognize the underlying error in this thinking: such properties only emerge if you have a plurality of atoms, or in some cases even by the interaction of different materials.
This concept thus commits the fallacy of division and the term is also used derivatively as a synonym for this fallacy.
Read more about this error under Fallacy of Division.