Following are definitions of a few terms. Much more complete glossaries can be found at these websites:
Face: The area of the dial where time is reckoned, with the hour and date lines; just like the face of a watch.
Furniture: Features on the sundial’s face that are not used for reckoning time. They often enhance the dial aesthetically. The EarthDial’s furniture includes the location, the year, the motto (“Two Worlds One Sun”), and any individual decorations. The MarsDial furniture includes the word Mars in many languages, planetary orbits, and mirror surfaces to observe the Martian sky.
Gnomon: The sundial’s shadow caster. It can be a stick, a triangle, or any number of other shapes depending on the shape of the shadow sought by the dial designer.
Gnomonicist: Someone who designs and enjoys sundials (who doesn’t?)
Motto: A saying inscribed on the sundial’s face to evoke deep or other thoughts
Nodus: Feature on a gnomon that allows viewers to see the shadow of a single point, as opposed to that of a post or edge. A nodus often enables the dial tell the date as well as the time.
Style: The edge of a triangular gnomon, which on dials of that type casts the shadow that is read to tell the time.
In 2016, The Planetary Society’s LightSail program will take the technology a step further.