Description: One nanometer is one-billionth of a meter. Its symbol is nm. A human hair is approximately 80,000–100,000 nm wide, about the same as the thickness of a piece of paper. A strand of human DNA is about 2.5 nm in diameter. A water molecule is less than 1 nm across. The wavelength of visible light can be measured in nm. Typically, the human eye can detect light with wavelengths between about 380 nm (violet) to 750 nm (red).

Term and definition status: This term and its definition have been approved by a research astronomer and a teacher

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