Particles

Particle, n–in nanotechnology, a small object that behaves as a whole unit in terms of its transport and properties.

It is further classified according to size: In terms of diameter, fine particles cover a range between 100 and 2500 nanometers, while ultrafine particles, on the other hand, are sized between 1 and 100 nanometers. Similarly to ultrafine particles, nanoparticles are sized between 1 and 100 nanometers, though the size limitation can be restricted to two dimensions. Nanoparticles may or may not exhibit size-related intensive properties that differ significantly from those observed in fine particles or bulk materials.

Source:
ASTM International. E 2456-06. Terminology for Nanotechnology