A dagger, or obelisk, U+2020 † dagger (HTML:
†), is a typographical symbol or glyph. The term "obelisk" derives from Greek ὀβελίσκος (obeliskos), which means "little obelus"; from Ancient Greek: ὀβελός (obelos) meaning "roasting spit". It was originally represented by the ÷ symbol and was first used by the Ancient Greek scholars as critical marks in manuscripts.
A double dagger or diesis, U+2021 ‡ double dagger (HTML:
‡), is a variant with two handles. Neither should be confused with the Christian cross symbol.
The dagger symbol originated from a variant of the obelus (plural: obeli), originally depicted by a plain line (-) or a line with one or two dots (÷). It represented an iron roasting spit, a dart, or the sharp end of a javelin, symbolizing the skewering or cutting out of dubious matter.
The obelus is believed to have been invented by the Homeric scholar Zenodotus as one of a system of editorial symbols. They were used to mark questionable or corrupt words or passages in manuscripts of the Homeric epics. The system was further refined by his student Aristophanes of Byzantium, who first introduced the asterisk and used a symbol resembling a ⊤ for an obelus; and finally by Aristophanes' student, in turn, Aristarchus, from whom they earned the name of 'Aristarchian symbols'.
While the asterisk (asteriscus) was used for corrective additions, the obelus was used for corrective deletions of invalid reconstructions. It was used when non-attested words are reconstructed for the sake of argument only, implying that the author did not believe such a word or word form had ever existed. Some scholars used the obelus and various other critical symbols, in conjunction with a second symbol known as the metobelos ("end of obelus"), variously represented as two vertically arranged dots, a γ-like symbol, a mallet-like symbol, or a diagonal slash (with or without one or two dots). They were used to indicate the end of a marked passage.
It was used much in the same way by later scholars to mark differences between various translations or versions of the Bible and other manuscripts. The early Christian Alexandrian scholar Origen (c. 184 – 253 AD) used it as a method of indicating differences between different versions of the Old Testament in his Hexapla. Epiphanius of Salamis (ca. 310–320 – 403) used both a horizontal slash or hook (with or without dots) and an upright and slightly slanting dagger to represent an obelus. St. Jerome (c. 347 – 420) used a simple horizontal slash for an obelus, but only for passages in the Old Testament. He describes the use of the asterisk and the dagger as: "an asterisk makes a light shine, the obelisk cuts and pierces."
Isidore of Seville (c. 560 – 636 AD) described the use of the symbol as follows: "The obelus is appended to words or phrases uselessly repeated, or else where the passage involves a false reading, so that, like the arrow, it lays low the superfluous and makes the errors disappear... The obelus accompanied by points is used when we do not know whether a passage should be suppressed or not."
Medieval scribes used the symbols extensively for critical markings of manuscripts. In addition to this, the dagger was also used in notations in early Christianity, to indicate a minor intermediate pause in the chanting of Psalms, equivalent to the quaver rest notation. It is also used to indicate a breath mark when reciting, along with the asterisk, it is thus frequently seen beside a comma.
In the 16th century, the printer and scholar Robert Estienne (also known as Stephanus in Latin and Stephens in English) used it to mark differences in the words or passages between different printed versions of the Greek New Testament (Textus Receptus).
The obelus was also occasionally used as a mathematical symbol for subtraction. It was first used as a symbol for division by the Swiss mathematician Johann Rahn in his book Teutsche Algebra in 1659. This gave rise to the modern mathematical symbol ÷.
Due to the variations as to the different uses of the different forms of obeli, there is some controversy as to which symbols can actually be considered obeli. The lemniscus (÷) and its variant, the hypolemniscus, is sometimes considered to be different from other obeli. And obeli may have referred strictly only to the horizontal slash and the dagger symbols.
Modern usage 
The dagger is usually used to indicate a footnote, in the same way an asterisk is. The dagger is only used for a second footnote when an asterisk is already used. A third footnote employs the double dagger. Additional footnotes are somewhat inconsistent and represented by a variety of symbols, e.g., parallels (||) and the pilcrow (¶), some of which were nonexistent in early modern typography. Partly because of this, superscript numerals have increasingly been used in modern literature in the place of these symbols, especially when several footnotes are required. Some texts use asterisks and daggers alongside superscripts, using the former for per-page footnotes and the latter for endnotes.
The dagger is also used to indicate death, extinction, or obsolescence. The asterisk and the dagger, when placed beside years, are used to indicate year of birth and year of death respectively. When placed immediately before or after a person's name, it indicates that the person is deceased. In this usage, it is referred to as the "death dagger". In the Oxford English Dictionary, the dagger symbol is used to indicate an obsolete word.
The dagger (†) should not be confused with the Christian cross (✝, U+271D), the character "box drawings light vertical and horizontal" (┼, U+253C), or other cross symbols. The double dagger should not be confused with the alveolar click ([ǂ], U+01C2), the Cross of Lorraine (☨, U+2628), or the patriarchal cross (☦, U+2626).
- In mathematics and, more often, physics, a dagger is used to denote the Hermitian adjoint of an operator; for example, A† denotes the adjoint of A. This notation is sometimes replaced with an asterisk, especially in Mathematics. An operator is said to be Hermitian if A† = A.
- In textual criticism and in some editions of works written before the invention of printing, daggers are used to enclose text that is believed not to be original.
- In biology, the dagger next to a taxon name indicates that the taxon is extinct.
- In cataloging, a double dagger is used to delimit MARC subfields.
- In chess notation, the dagger may be suffixed to a move to signify the move resulted in a check, and a double dagger is used to denote checkmate. This is a stylistic variation on the more common '+' (plus sign) for a check and '#' (octothorpe) for checkmate.
- In chemistry, the double dagger is used in chemical kinetics to indicate a transition state species.
- In psychological statistics the dagger is used to indicate that a difference between two figures is not significant to a p<0.05 level, however is still considered a "trend" or worthy of note. Commonly this will be used for a p-value between 0.1 and 0.05.
- On a cricket scorecard or team list, the dagger indicates the team's wicket-keeper.
- In military history, a dagger is often placed next to the name of a commander who is killed in action.
- The asteroid 37 Fides, the last asteroid to be assigned an astronomical symbol before the practice faded, was assigned the dagger.
- In philology, the dagger indicates an obsolete form of a word or phrase.
- In the early printings of the King James Bible a dagger is used to indicate a literal translation of a word or phrase is to be found in the margin. When used the margin begins with an abbreviation (Heb. Gk. Chald. Lat.) for the original language.
- In the Geneva Bible a double dagger is used to indicate a literal translation of a word or phrase is to be found in the margin. When used the margin begins with an abbreviation (Heb. Gk. Chald. Lat.) for the original language.
While daggers are freely used in English-language texts, they are often avoided in other languages because of their similarity to the Christian cross. In German, for example, daggers are commonly employed only to indicate a person's death or the extinction of a word, language, species or the like.
See also 
- "obelus". Oxford Dictionaries Online. April 2010.
- Merriam-Webster's collegiate dictionary. Merriam-Webster, Inc. 2003. p. 855. ISBN 978-0-87779-809-5.
- William Harrison Ainsworth, ed. (1862). The New monthly magazine 125. Chapman and Hall. p. 1.
- Harold P. Scanlin (1998). "A New Edition of Origen's Hexapla: How It Might Be Done". In Alison Salvesen. Origen's Hexapla and fragments: papers presented at the Rich Seminar on the Hexapla, Oxford Centre for Hebrew and Jewish Studies, 25th-3rd August. Mohr Siebeck. p. 439. ISBN 978-3-16-146575-8.
- Richard Barrie Dobson (2000). Encyclopedia of the Middle Ages, Volume 2. Routledge. p. 1038. ISBN 978-1-57958-282-1.
- Johann Georg Hamann, Kenneth Haynes (2007). Writings on philosophy and language. Cambridge University Press. p. 94. ISBN 978-0-19-920246-1.
- Paul D. Wegner (2006). A student's guide to textual criticism of the Bible. InterVarsity Press. p. 194. ISBN 978-0-19-814747-3.
- George Maximilian Anthony Grube (1965). The Greek and Roman critics. Hackett Publishing. p. 128. ISBN 978-0-87220-310-5.
- "BHS Critical Apparatus". A Simplified Guide to BHS.
- "Hexapla". The Catholic Encyclopedia. Retrieved August 27, 2011.
- Ernst Würthwein (1995). The text of the Old Testament: an introduction to the Biblia Hebraica. Wm. B. Eerdmans Publishing. p. 58. ISBN 978-0-8028-0788-5.
- "The Meaning of the Markings, Critical Marks and Marginal Notes: Their True Significance". The Nazaroo Files. February 19, 2009. Retrieved August 27, 2011.
- Daniel H. Garrison (2004). The student's Catullus. University of Oklahoma Press. p. 184. ISBN 978-0-8061-3635-6.
- R. Grant Jones (2000). "The Septuagint in Early Christian Writings". Notes on the Septuagint. p. 4.
- William Smith & Henry Wace, ed. (1882). A Dictionary pf Christian Biography, Literature, Sects and Doctrines; During the First Eight Centuries. Being A Continuation of 'The Dictionary of the Bible'. Volume III. Hermogenes–Myensis. John Murray.
- Kay Kaufman Shelemay, Peter Jeffery, & Ingrid Monson (1994). "Oral and written transmission in Ethiopian Christian chant". In Iain Fenlon. Early Music History: Studies in Medieval and Early Modern Music. Cambridge University Press. p. 81. ISBN 978-0-521-45180-2.
- "Obelisk, Obelus, Dagger". seiyaku.com. Retrieved August 26, 2011.
- David Martin (French divine) (1719). "Chap. X. Of the Obelus and Semicircle, the passage of St. John is mark'd with in Stephen's Edition". A critical dissertation upon the seventh verse of the fifth chapter of St. John's First Epistle: there are three that bear record in Heaven, &c. : wherein the authentickness of this text is fully prov'd against the objections of Mr. Simon and the modern Arians. Printed for William and John Innys. p. 65.
- "Math Words, pg 7". Math Words Alphabetical Index. Retrieved August 26, 2011.
- Eric Partridge (2004). You Have a Point There: A Guide to Punctuation and Its Allies. Routledge. p. 235. ISBN 978-0-203-37992-9.
- Hoefler, Jonathan (4 June 2009). "House of Flying Reference Marks, or Quillon & Choil". Hoefler & Frere-Jones.
- John D. Reynolds (2002). Handbook of fish biology and fisheries. Wiley-Blackwell. p. 108. ISBN 978-0-632-05412-1.
- Colin Tudge (2000). "Conventions for Naming Taxa". The variety of life: a survey and a celebration of all the creatures that have ever lived. Oxford University Press. p. 93. ISBN 978-0-19-860426-6.
- "Guide to the Third Edition of the OED". Oxford University Press. Retrieved August 26, 2011.
- Elizabeth Knowles (2006). Oxford dictionary of phrase and fable. Oxford University Press. ISBN 978-0-19-920246-1.
- Alastair Campbell (2004). The digital designer's jargon buster. The Ilex Press Ltd. p. 84. ISBN 978-1-904705-35-2.
- John Lennard, ed. (2005). "Punctuation". The poetry handbook: a guide to reading poetry for pleasure and practical criticism. Oxford University Press. p. 140. ISBN 978-0-19-926538-1.
- "Author Line". The APS Online Style Manual. Retrieved August 26, 2011.
- Weisstein, Eric W., "Dagger", MathWorld.
- David L. Hull (1990). Science as a process: an evolutionary account of the social and conceptual development of science. University of Chicago Press. p. 254. ISBN 978-0-226-36051-5.
- "Cricket Scorecard: 43rd Match, Super Eights: Australia v Sri Lanka at St George's". ESPN Cricinfo. 2007-04-16.