The science of manipulating materials on an atomic or molecular scale, especially to build microscopic devices such as robots.

Nanotechnology, or *nanotech* for short, deals with matter at a level that most of us find hard to imagine, since it involves objects with dimensions of 100 billionths of a meter (1/800th of the thickness of a human hair) or less. The chemical and physical properties of materials often change greatly at this scale. Nanotechnology is already being used in automobile tires, land-mine detectors, and computer disk drives. *Nanomedicine* is a particularly exciting field: Imagine particles the size of a blood cell that could be released into the bloodstream to form into tiny robots and attack cancer cells, or “machines” the size of a molecule that could actually repair the damaged interiors of individual cells.

One billionth of a second.

The nonserious use of *nanosecond* is probably much more common than the proper technical use. In measurement terms such as *nanosecond*, *nanogram*, and *nanometer*, *nano-* means “billionth”; in other kinds of words, its meaning isn't quite so precise. In computers, the speed of reading and writing to random access memory (RAM) is measured in nanoseconds. By comparison, the speed of reading or writing to a hard drive or a CD-ROM player, or for information to travel over the Internet, is measured in *milliseconds* (thousandths of a second), which are a million times longer than nanoseconds.

An arrangement, structure, or part of something of molecular dimensions.

Two important types of nanostructure are *nanocrystals* (tiny crystals, often of semiconducting material) and *nanotubes* (tiny tubes, usually of pure carbon). Nanocrystals made from semiconductors change color depending on their size, and are being used for such tasks as detecting viruses in living cells. Nanotubes can conduct enormous amounts of electrical current, far more than metal wires. They are the basic material of tiny “paper” batteries, which can be rolled, folded, or cut while still producing power. Nanotubes are also now being used in materials for lightweight tennis rackets and golf clubs, and may soon enable the manufacture of TV screens no thicker than a film.

A tiny particle whose size is measured in billionths of a meter.

Nanoparticles of a material usually have very different qualities from those that the material has at its ordinary scale, which is one reason why there's such excitement about the possibilities for how they might be used in future technologies. Many uses have already been developed. Aluminum nanoparticles added to rocket fuel can make the fuel burn twice as fast and release much more energy. Silicon nanoparticles are increasing the energy efficiency of solar cells by allowing the energy from ultraviolet light to be captured for the first time. Other nanoparticles are now helping prevent rust in metals, produce stronger batteries, enhance the diagnosis of cancer, and improve the filtering of water, and the number of other applications is growing fast.

Beyond what is needed; extra.

Since the Latin *fluere* means “to flow” (see FLU), you can think of *superfluous* as describing a river with so much water that it's overflowing its banks. The word is used in all kinds of contexts. Superfluous characters in computer code may keep it from working. Most of the buttons on a remote control may strike us as superfluous, since we never use them. When a situation “speaks for itself,” any comment may be superfluous. And whenever you yourself are feeling superfluous, as in a “Two's company, three's a crowd” situation, it's probably time to leave.

Incapable of being solved or overcome.

From its roots, the literal meaning of *insuperable* would be something like “un-get-overable” ; *insurmountable* is a fairly exact synonym. *Insuperable* is used to describe obstacles, difficulties, barriers, obstructions, problems, and objections. Americans love stories of people who succeed in spite of terrible handicaps, whether as a result of physical limitations, prejudice, poverty, or lack of opportunity; such rugged spirits may be called *indomitable*, “incapable of being subdued.”

To take the place of; to replace with something newer or more useful.

The Latin word *supersedere* means “sit on top of”—which is one way of taking someone else's place. Your boss may send around a memo that supersedes the memo she sent the day before (the one with all the errors in it). Every time the first-class postage rate goes up, the new stamps supersede the old ones. In science, a new theory often supersedes an older one; for example, the theory that a characteristic you acquire during your lifetime can be passed on biologically to your children (called *Lamarckism*) was superseded by Darwin's theory of evolution. Watch out when spelling this word; *supersede* is practically the only English word that ends in *-sede*.

Supreme, excellent.

*Superlative* may sound high-flown when compared with a synonym like *outstanding*, but if your next paper comes back from your teacher with the comment “ Superlative work!” at the top you probably won't complain. Since *superlative* means “best, greatest,” it makes sense that *superlative* is also a term used in grammar for the highest degree of comparison. So for the adjective *simple*, for example, the comparative form is *simpler* and the superlative form is *simplest*; and for the adverb *boldly*, the comparative form is *more boldly* and the superlative is *most boldly*.