A relationship used between material continuants where one is composed of the other.

If C and C1 are continuant classes, then C has_component_part C1 means that every instance “c” of C is prepared from some instances “c1” of C1 and a significant material portion of c1 becomes part of the constituting material of c when c begins to exist.

In the NPO, this relationship is mostly used to describe the composition of nanoparticle formulations or nanoparticles.