from the GNU version of the Collaborative International Dictionary of English.

  • noun John Dalton, scientist, born 1766, died 1844.
  • noun a unit of mass, approximately 1.66 x 10-24 grams; -- it is approximately equal to the mass of one hydrogen atom, but the exact value differs slightly as used in physics and chemistry. It is used mostly to describe the size of proteins and nucleic acids in biochemistry.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • noun physics the atomic mass unit

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • noun English chemist and physicist who formulated atomic theory and the law of partial pressures; gave the first description of red-green color blindness (1766-1844)


from The American Heritage® Dictionary of the English Language, 4th Edition

[After John Dalton.]



Log in or sign up to get involved in the conversation. It's quick and easy.

  • an alternate name for the unified atomic mass unit (u or amu). The dalton is often used in microbiology and biochemistry to state the masses of large organic molecules; these measurements are typically in kilodaltons (kDa). It seems necessary to have such a unit, since "kilo-amu" would be such a clumsy name. The SI accepts the dalton as an alternate name for the unified atomic mass unit and specifies Da as its proper symbol. The unit honors the English chemist John Dalton (1766-1844), who proposed the atomic theory of matter in 1803.

    January 21, 2008