What does angstrom mean?
The angstrom is a very small unit of length equal to one ten-billionth of a metre (10⁻¹⁰ m), or one tenth of a nanometre. It takes its name from Anders Jonas Ångström, the nineteenth-century Swedish physicist who pioneered spectroscopy. Although it is not part of the International System of Units, the angstrom remains firmly entrenched in fields that deal with atomic-scale dimensions, particularly spectroscopy, crystallography, and molecular biology. Chemists use it to state bond lengths — a typical carbon–carbon bond is around 1.5 angstroms — while physicists use it to describe the wavelengths of visible light and X-rays. Its enduring popularity stems from convenience: most atomic distances fall conveniently between 0.5 and 5 angstroms, making numbers easy to grasp. The unit's official status has gradually given way to the picometre and nanometre in formal standards, but in everyday scientific communication the angstrom persists as a practical, well-understood measure of the very small.
nounA unit of length equal to one ten-billionth of a metre (10⁻¹⁰ m), used especially to express the wavelengths of light and X-rays and the sizes of atoms and molecules. It is not an SI unit, but it remains in common scientific use.
- A unit of length equal to 10⁻¹⁰ metre, used in spectroscopy and crystallography to express wavelengths and atomic dimensions.
"The bond between the two hydrogen atoms measures about 0.74 angstroms."
"Visible light has wavelengths ranging from about 4,000 to 7,000 angstroms."
"The crystal lattice spacing was determined to be 3.6 angstroms."
Regular plural; used with numerals above one, as in 'two angstroms'.
"The layer was only a few angstroms thick."
Named after a 19th-century Swedish physicist, the angstrom is so small that a human hair spans roughly half a million of them — yet it's still the unit chemists reach for when measuring atoms.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of angstrom
The word angstrom comes from the name of Anders Jonas Ångström (1814–1874), the Swedish physicist whose precise measurements of solar spectral lines made him a founding figure of spectroscopy. The unit was named in his honour in the late nineteenth century, and its symbol Å preserves the Swedish letter in his surname. It belongs to the family of units named after scientists, like the watt, volt, and kelvin.
How angstrom is actually used
The symbol is Å (a capital A with a ring above it). The word is usually written 'angstrom' without a capital letter, though it derives from a proper name. It is technically non-SI but is accepted for use in specialized fields such as spectroscopy, crystallography, and structural biology. Plural: angstroms; occasionally 'angstrom' is treated as invariant after numerals.
Easily confused with angstrom
An angstrom is a tiny unit (10⁻¹⁰ m) for atomic scales, while an astronomical unit is a vast one (~150 million km) for distances within the solar system.