The new word "Nanomaterial" literally means that it is the material with at least one of its dimensions in the range of a nanometer.
The material need not be so small that it cannot be seen; it can be a large surface or a long wire whose thickness is in the scale of nanometers; the range could be 1 to 103 nanometers.
However this is only a trivial guess answer expected from a student of general education.
The Nanomaterials are of our interest not simply because their size is exactly or roughly one nanometer as suggested by the name. They are so named because the size, at and below which many materials exhibit interesting properties , falls on the scale of a few orders of a nanometer. We have to seek the speciality of this small size to get the most apppropriate difinition of the Nanomaterial: Suppose we cut any solid material of the some volume, say gold biscuit of 100 centimetre cube, into pieces: then each piece will have the same properties of the gold but for, ofcourse, the size. If they are cut further, the small pieces still possess the same qualities of the gold. Thus the macroscopic solid pieces of the materials possess size independent properties. The density, color, hardness, melting point, resistivity etc of the material do not depend on the size. Now imagine that we can cut the material indefinitely into pieces of any small size that we wish; these pieces may be so small that we cannot see them individually. Also assume that we can pack them together like a spoonful powder so that we can see them collectively. Then it has been found that below a particular size of each piece, the properties of the material depend on the size; the same gold pieces, each smaller than a particular size, will no longer be yellow; they may be red or violet collectively, depending on the particle size. This surprising fact is illustrated by the colour photos of samples.
Now-a-days to divide the matter into extremely small particles is not at all hypothetical; we have well established methods of preparing such small pieces and utilizing their special properties; in fact, this is the nanotechnology attracting top class industries throughout the globe to invest billions of dollars expecting roaring profits.
Now we may state the most appropriate definition:
A nanomaterial is that which is made up of particles each of size small enough to exhibit size dependent properties and large enough to form a solid state structure.
This matter will be in the gaseous state if its atoms or molecules are free from each other. In this field of nanotechnology, we are interested in solid state materials; hence nanoparticles are necessarilylarger than diatomic or triatomic molecules. They measure intermediate in size and posses transitional properties between isolated small molecules and bulk materials of the same composition. These new properties of the materials are size controlled and exploited to design the nanodevices, the smallest human made solid state structures of the present day technology. Biomaterials are naturally existing nanomaterials. Many universities, research institutes and prospective industries are preparing a variety of nanomaterials.
