One answer is available in the European Commission Communication “Nanosciences and Nanotechnologies: An action plan for Europe 2005-2009”, of June 2005:

“Nanosciences and Nanotechnologies (N&N) are new approaches to research and development that concern the study of phenomena and manipulation of materials at atomic, molecular and macromolecular scales, where properties differ significantly from those at a larger scale.”

Nanoscience and Nanotechnology is the understanding and control of matter at dimensions of roughly 1 to 100 nanometers, where unique phenomena enable novel applications. Encompassing nanoscale science, engineering and technology, nanotechnology involves imaging, measuring, modeling, and manipulating matter at this length scale. Nanotechnology R&D is directed toward understanding and creating improved materials, devices, and systems that exploit these new properties.