A square nanometer (often abbreviated as nm²) is a unit of area in the International System of Units (SI) and is used to describe extremely small areas, especially in the context of nanotechnology and scientific research.
One square nanometer is equal to one billionth of a square meter (1 x 10^-9 m²). In other words, it takes one billion square nanometers to make up one square meter.
To give you a sense of scale, a square nanometer is incredibly tiny. It's often used to describe the size of individual atoms, molecules, or the features on nanoscale devices. Nanotechnology deals with structures and materials on this extremely small scale, where traditional units of area, like square meters or even square millimeters, are impractical.
A circular mil (often abbreviated as cmil or kcmil) is a unit of area used primarily in the United States for measuring the cross-sectional area of a round wire or cable. It is a convenient unit for specifying the size of electrical conductors.
One circular mil is equal to the area of a circle with a diameter of one mil (1/1000th of an inch) or approximately 0.000000506707 square inches (in²). In metric units, one circular mil is approximately equal to 0.000001273 square millimeters (mm²).
Circular mils are commonly used in the American Wire Gauge (AWG) system to specify wire sizes. The AWG system assigns a unique number to each wire size, and this number is related to the wire's cross-sectional area in circular mils. For example, a larger AWG number corresponds to a smaller wire size with fewer circular mils, while a smaller AWG number corresponds to a larger wire size with more circular mils. This system allows for easy reference and selection of wire sizes for various electrical applications.