nanogram

This term is used almost exclusively in scientific, medical, and laboratory contexts, particularly in pharmacology, biochemistry, and analytical chemistry. It describes an extremely minute quantity of a substance, often used when measuring hormone levels, drug concentrations in the blood, or trace contaminants in a sample.

Because it represents such a small scale, it is typically paired with high-precision instruments like mass spectrometers. In common parlance, it is rarely used outside of technical reports or academic papers, as the quantity is too small for intuitive human perception.