Analemma, special 8 shaped curve that corrects Local time to Standard time.
Analemmatic Dials are a particular type of azimuth dial.
Apparent Time is the time shown by a sundial placed exactly on a standard time meridian. It is irregular through the year with respect to standard time.
Astronomical Hours are the hours commonly indicated by a sundial (standard hours). They start from midnight. The lines representing the astronomical hours converge into the centre of the dial.
Azimuth Dials determine the hours from the variation of the azimuth of the sun
Babylonian Hours, similar to Italian hours but beginning from sunrise (hour 0).
Canonical Hours , system of timekeeping used in convents in the Middle Ages.
Centre of a dial, point of meeting of all astronomical hours where the style is applied.
Declination means the angle in degrees between the east - west line and the plane of the dial. A plane facing south has zero declination; facing east it has – 90° of declination and 90° if it looks west.
Dialist, sundial maker or sundial calculator, gnomonist
Elevation Dials are sundials that indicate the hour by the elevation of the sun above the horizon.
Equation of Time, the difference between apparent time and mean time.
False Pillar or False Style, a particular type of gnomon neither style nor pillar.
The foot of the dial, is the point of the substyle perpendicular to the apex of the style.
Gnomon, generic term used to refer to any object that casts its shadow to indicate the hour.
Gnomonics, the science of sundials.
Gnomonist , sundial maker or sundial calculator, dialist.
Height of the style, angular distance between the style and the substyle.
Inclination (British), see reclination.
Italic Hours were used in past centuries in Europe, especially in Italy. They are 24, similarly to astronomical hours, but are measured from sunset (24th hour).
Local Time is the apparent time with reference to a particular longitude, not necessarily that of the exact standard time meridian.
Mean Time, is the constant time determined by a fictitious sun moving over the celestial equator.
The meridian Line or 12 o’clock line indicates the local noon.
Noon, instant of midday.
Perpendicular Style or pillar. It indicates the hour or the sun’s declination by the tip of its shadow.
Pillar or perpendicular style. It indicates the hour or the sun’s declination by the tip of its shadow.
Planetary Hours follow the division of temporary hours but include areas subject to "masters", the planets that dominate the hours and the days of the week.
Reclination (USA term) of the dial means the angle between the line of greatest slope of a dial plate and the plumb- line.
Standard Time, is the time (mean time) in use in a Standard Time Zone.
Style is the edge, pointed to the celestial pole, of the gnomon. The shadow of the style tells the hour by using the sun’s hour angle.
Substyle Distance, angular distance between the meridian line and the substyle.
Substyle is the line, perpendicular projection of the style, on the dial plate. It passes through the centre and the foot.
Sundial is a shadow clock that exploits the sun’s light through the day or, even, through the year to tell the time.
Temporary or Temporal Hours were in use at the time of Greeks and Romans, but used through the Middle Ages. They divide the day, from sunrise to sunset, into 12 even parts independently of the season. The hour of sunrise is 0 and that of sunset is 12. 6 o’clock temporary hour always coincides with the solar noon.