ortho

ortho (plural orthos)

1. (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”, in Chemical News‎^[269]:

     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 : […] .

   • 2009 February 27, P. Neumann et al., “Response to Comment on "Multipartite Entanglement Among Single Spins in Diamond"”, in Science‎, volume 323, number 5918, DOI:10.1126/science.1168459:

     Similarly, it also does not make sense to call the spin states of ortho and para hydrogen entangled.

2. (astronomy) A certain type of flat eyepiece
   • 1998, Terence Dickinson, NightWatch: A Practical Guide to Viewing the Universe, page 76:

     Orthos are excellent eyepieces, still preferred by some backyard astronomers for medium- and high-power applications, especially planetary observing.

3. (photography, dated) An orthochromatic plate
   • 1908 June, Charles F. Rice, “On the Use of Orthochromatic Plates”, in Photographic Times, page 174:

     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.

4. (imaging) An orthophoto
   • 2001, Drew Decker, GIS Data Sources, page 105:

     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.

5. (medicine) Orthopedics.

• thoro

From orthodontist.

• IPA^(key): /ˈɔr.toː/
• Hyphenation: or‧tho
• Rhymes: -ɔrtoː

ortho c (plural ortho's, diminutive orthootje n)

1. (informal) Clipping of orthodontist, orthodontiste.