Pages: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Introduction    Dial types    Hours (types of)    Time (types of)    Illustration
Symbols    Equations    Biographies    Chronology    Sources    Appendices                                            

A sourcebook of dialling data

Pillar sundial


(available only in printed form – see Publications)

The first edition of the Glossary was well received but, naturally, many readers found omissions or  inconsistencies in some of the entries.  These have now hopefully been addressed, although a work like this will never be completed.  The major areas added for this edition are a set of thumbnail biographies of the major players in the development of dialling, an expansion of the Equations section to include more dial types, and a major increase in the number of appendices providing solar and other data.
March 2004


Several letters to the BSS Bulletin in 1999 suggested that a sundialling glossary would be useful in furthering the Society’s aims.  It is hoped that this resulting glossary will fulfil two objectives.  The first of these is to provide newcomers to dialling with a reference document which will explain the many strange terms or unusual usages of common words which they will come across in the dialling literature.

The second objective is to try to produce definitive meanings of the terms which diallists sometimes use rather loosely, and which can therefore lead to some confusion.  Thus when several words have the same meaning, the preferred use is described here.  Likewise, an attempt has been made to produce a standardised set of symbols for the most widely used terms in dialling equations.

Choices between different meanings have been made on the basis of adopting the most common modern usage found in the literature (particularly those items shown in the Sources section) as long as this does not produce confusion.  Alternative usages, spellings or conventions which may be met, particularly in early dialling works, have been given where possible, but it is hoped that future authors will adopt the preferred definitions given here.

As English is used in countries other than the UK, there may be alternative definitions overseas.  However, this glossary has been assembled with collaboration from the North American Sundial Society and, via the medium of the internet, diallists worldwide, so it is not expected that there will be major differences in terminology throughout the majority of the English-speaking world.

May 2000


The glossary contains mainly terms which are directly related to dials and dialling.  Additionally, excursions into the fields of astronomy, horology, optics and solar sciences have been made where it seems useful.  Some comments on the history of dialling are made and various solar data are given in the appendices.


Words in italics refer to entries in this glossary or other internal references.

Bold text indicates a definition.

~ indicates a repeat of the entry word.

Symbols in square brackets [x, X ] give the preferred symbol and abbreviation.  See section on Symbols for a full list.

Alternative spellings or terms to the preferred ones are shown in brackets thus: {dialing}.

Pronunciation of unusual words is shown with a simplified phonetic scheme thus: gnomon: (pron. no-mon).  If no pronunciation is given for an entry, it is pronounced as it is written (following normal Oxford Dictionary rules for English pronunciation).


I would like to thank the numerous members of the BSS and the NASS who helped with the definitions of terms, and who provided encouragement to the project.  These include, in no particular order, Margaret Stanier, David Young, Patrick Powers, John Carmichael, Harvey Frey, Tony Wood, John Ingram, Doug Bateman, Frank and Rosie Evans, David Scott, Robert Terwilliger, Fer de Vries, Fred Sawyer, Gianni Ferrari, Tony Baigent, Chris Lusby Taylor, Mac Oglesby, Vit Planocka, Daniel Wenger, Gordon Taylor, Michael Lowne, Sara Schechner, Robert van Gent, Tony Moss, Allan Mills, Thibaud Taudin-Chabot, Gerald Stancey, Mike Cowham, Gloria Clifton, Peter Ransom, George Huxley, Chris Daniel, Jill Wilson, Mike Shaw, Michael Harley, Paul Zoller, Tony Belk.

A note on the Southern Hemisphere.

This glossary has been written primarily for the Northern Hemisphere, since this is where the majority (but not all) of the BSS membership resides.  For horizontal dials in the Southern Hemisphere the gnomons point to the S celestial pole, and the hour numbers run anti-clockwise rather than clockwise.  The notation and equations used in the glossary are consistent as long as the sign conventions are followed, but the reader must mentally change N to S in the text.


The second edition of the Glossary is published by the British Sundial Society as a printed book which is now available.


It is proposed to update this glossary periodically, so that it will develop along with the science of dialling. If you have any comments, corrections or additions, please email the editor or write to the address below.
John Davis
Orchard View, Tye Lane
Ipswich IP8 4LD

Pages: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Introduction    Dial types    Hours (types of)    Time (types of)    Illustration
Symbols    Equations    Biographies    Chronology    Sources    Appendices