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.
The "acre (US survey)" is a unit of area used specifically in the United States for land surveying and legal property descriptions. It is different from the standard acre used in other parts of the world. The U.S. survey acre is based on the U.S. survey foot, which is a historical unit of length used in land surveying in the United States. The U.S. survey foot is slightly different from the international foot.
One acre (US survey) is equal to approximately 4,046.872609874252 square meters (m²) or about 0.40468726 hectares (ha).
This unit is used in various land-related applications, especially in the United States, where the U.S. survey acre is employed for legal and historical reasons in land surveys, property descriptions, and land records. It's important to be aware of the specific units being used when dealing with land measurements in the United States to avoid discrepancies or errors.