ortho

noun6

1. •
   An isomer of a benzene derivative having two substituents adjacent on the ring.

   • 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 : […]. — 1887
2. •
   Clipping of orthopedics.
3. •
   Clipping of orthophoto.

   • 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. — 2001
4. •
   A certain type of flat eyepiece.

   • Orthos are excellent eyepieces, still preferred by some backyard astronomers for medium- and high-power applications, especially planetary observing. — 1998
5. •
   Clipping of orthography.
6. •
   (old-fashioned) An orthochromatic plate.

   • 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. — 1908