(chemistry) An isomer of a benzene derivative having two substituents adjacent on the ring
1887, December 21, Thomas M. Morgan, On Some Derivatives of Ortho-Nitro-Cinnamic Acid, When the cinnamic acid had been nitrated the ortho was separated from the para, by suspending in alcohol and leading hydrochloric acid gas into the mixture : the alcohol grows warm, and the ethers as they form dissolve ; but as the solution cools the para ether almost completely separates, and on filtering and distilling a residue is obtained consisting of ethyl-ortho-nitro-cinnamate ... .
February 27, Similarly, it also does not make sense to call the spin states of ortho and para hydrogen entangled.
1998, Terence Dickinson, NightWatch: A Practical Guide to Viewing the Universe, Orthos are excellent eyepieces, still preferred by some backyard astronomers for medium- and high-power applications, especially planetary observing.
1908, June, Charles F. Rice, On the Use of Orthochromatic Plates, Wherever the exposure is likely to be cut short— and this includes all high speed work and most portraiture — the ortho is not so suitable as the ordinary plate.
2001, Drew Decker, GIS Data Sources, The typical orthophoto building process is a long one, however, and the photography that the orthos are based may be several years old before an orthophoto is ready for distribution.
