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{{Short description|Mark made as a proof of identity and intent}}
{{Distinguish|Autograph}}
{{for|the use of signatures within the Wikipedia community|Wikipedia:Signature|selfref=y}}
{{other uses}}
{{pp|small=yes}}
{{More citations needed|date=April 2018}}
[[Image:JohnHancocksSignature.svg|thumb|300px| [[John Hancock]]'s signature is the most prominent on the [[United States Declaration of Independence]] and the [[Articles of Confederation]]. The name "John Hancock" or just "Hancock" has become a synonym for "signature" in the United States.<ref>{{cite web|title=John Hancock|url=http://www.merriam-webster.com/dictionary/john%20hancock|website=Merriam-Webster|access-date=2 August 2014}}</ref>]]

A '''signature''' ({{IPAc-en|ˈ|s|ɪ|ɡ|n|ɪ|tʃ|əɹ|,_|ˈ|s|ɪ|ɡ|n|ə|tʃ|əɹ}}; from {{langx|la|signare}}, "to sign") is a depiction of someone's name, nickname, or even a simple "X" or other mark that a person writes on documents as a proof of identity and intent. Signatures are often, but not always, [[Handwriting|handwritten]] or stylized. The writer of a signature is a '''signatory''' or '''signer'''. Similar to a handwritten signature, a '''signature work''' describes the work as readily identifying its creator. A signature may be confused with an [[autograph]], which is chiefly an artistic signature. This can lead to confusion when people have both an autograph and signature and as such some people in the public eye keep their signatures private whilst fully publishing their autograph.

==Function and types==
===Identification===
[[Image:Autograph of Benjamin Franklin.svg|thumb|Signature of [[Benjamin Franklin]] (1706–1790)]]
[[Image:Farah_Pahlavi_signature.svg|thumb|Signature of [[Shahbanu|Empress]] [[Farah Pahlavi]] of [[Iran]] (1938–) in [[Persian language|Persian]] handwriting]]
[[Image:Печат светог Саве.svg|thumb|Signature of [[Sava I of Serbia]] (1169/1174–1236), the first [[Archbishop of Serbia]], in the [[Cyrillic alphabet]]. Here, the letters [[А]] and [[В]] are combined into a single [[Digraph (orthography)|digraph]]]]

The traditional function of a signature is to permanently affix to a document a person's uniquely personal, undeniable self-identification as physical evidence of that person's personal witness and certification of the content of all, or a specified part, of the document. For example, the role of a signature in many consumer [[contracts]] is not solely to provide evidence of the identity of the contracting party, but also to provide evidence of deliberation and informed consent.

In the United States, signatures encompass marks and actions of all sorts that are indicative of identity and intent. The legal rule is that unless a statute specifically prescribes a particular method of making a signature it may be made in any number of ways. These include by a mechanical or rubber stamp [[facsimile]]. A signature may be made by the purported signatory; alternatively someone else duly authorized by the signatory, acting in the signer's presence and at the signatory's direction, may make the signature.<ref>80 [[Corpus Juris Secundum]], Signatures, sections 2 through 7</ref>

Many individuals have much more fanciful signatures than their normal [[cursive]] writing, including elaborate [[Ascender (typography)|ascenders]], [[descender]]s and exotic [[wiktionary:flourish|flourish]]es, much as one would find in [[calligraphic]] writing. As an example, the final "k" in [[John Hancock]]'s famous signature on the US Declaration of Independence loops back to underline his name. This kind of flourish is also known as a ''[[wikt:paraph|paraph]]'', a [[French language|French]] term meaning flourish, initial or signature. The paraph is used in [[graphology]] analyses.

Several cultures whose languages use writing systems other than alphabets do not share the Western notion of signatures per se: the "signing" of one's name results in a written product no different from the result of "writing" one's name in the standard way. For these languages, to write or to sign involves the same written characters. 
  
===Mark in lieu of signature <span class="anchor" id="Signature (mark)"></span>===
[[File:India 1952 2r stamped paper.jpg|thumb|Fingerprints may be used instead of signatures where the signer is illiterate, such as this Indian legal document from 1952]]
In some jurisdictions, an [[illiterate]] signatory can make a "mark" (often an "X" but occasionally a personalized symbol) on legal documents, so long as the document is countersigned by a literate witness.<ref>{{cite web |title=Horton v. Murden, 117 Ga. 72 |url=https://cite.case.law/ga/117/72/ |website=Caselaw Access Project |publisher=Harvard Law School |access-date=10 October 2022 |date=1903}}</ref> Courts in [[England and Wales]] are generally likely to recognise such a mark as legally valid.<ref>Gill, C., [https://www.walkermorris.co.uk/comment-opinion/law-commission-report-on-electronic-signatures/ Law Commission report on electronic signatures], ''Walker Morris'', published on 26 September 2019, accessed on 15 June 2025</ref> In some countries, illiterate people place a thumbprint on legal documents in lieu of a written signature.

===Mechanically produced signatures===
{{Main|Autopen}}
[[File:Xu yin Yongyu.jpg|right|thumb|130px|{{zh|labels=no|c=徐永裕印|p=Xú Yǒngyù yìn}}, rotating character seal of {{Zh|p=Xú Yǒngyù|labels=no}}]]
Special signature machines, called [[autopen]]s, are capable of automatically reproducing an individual's signature. These are typically used by people required to sign a lot of printed matter, such as celebrities, heads of state or CEOs.<ref>{{cite web| url = https://www.politico.com/story/2013/01/autopen-barack-obama-10-facts-085720| title = 10 facts about the 'autopen' - POLITICO| website = [[Politico]]| date = 3 January 2013}} </ref> More recently, [[Member of Congress|Members of Congress]] in the United States have begun having their signature made into a [[TrueType]] font file. This allows staff members in the Congressman's office to easily reproduce it on correspondence, legislation, and official documents. In the East Asian languages of [[Chinese language|Chinese]], [[Japanese language|Japanese]], and [[Korean language|Korean]], people traditionally use stamp-like objects known as ''name-[[seal (East Asia)|seal]]s'' with the name carved in ''tensho'' script (''[[seal script]]'') in lieu of a handwritten signature.{{Citation needed|date=October 2014}}

===Wet signatures===
A wet signature is a person's name written in their own hand with ink. Some government agencies require that professional persons or official reviewers sign originals and all copies of originals to authenticate that they personally viewed the content. In many countries, signatures must be made, witnessed and recorded in the presence of a [[notary public]] to carry legal force in specific contexts. In the United States this is prevalent with architectural and construction plans. Its intent is to prevent mistakes or fraud but the practice is not known to be effective.{{citation needed|date=August 2017}}

===Detection of forged signatures===
{{see|Postal voting in the United States#Signature verification process}}

Handwriting experts say "it is extremely difficult for anyone to be able to figure out if a signature or other very limited writing sample has been forged."<ref name="prop">{{Cite web |title=Handwriting Disputes Cause Headaches for Some Absentee Voters |url=https://www.propublica.org/article/handwriting-disputes-cause-headaches-for-some-absentee-voters |last=Armitage |first=Susie  |date=2018-11-05 |website=ProPublica |language=en |access-date=2020-06-01}}</ref>
High volume review of signatures, to decide if a signature is true or forged, occurs when election offices decide whether to accept [[absentee ballot]]s arriving from voters,<ref name="ncsl-allmap">{{Cite web |title=Voting Outside the Polling Place: Absentee, All-Mail and Other Voting at Home Options |url=https://www.ncsl.org/elections-and-campaigns/voting-outside-the-polling-place |website=[[National Conference of State Legislatures]] |access-date=2024-11-05 }}{{void|comment|Fabrickator|original url: https://www.ncsl.org/research/elections-and-campaigns/absentee-and-early-voting.aspx}}</ref>
and possibly when banks decide whether to pay [[Cheque#Cheque fraud|checks]].<ref name="sqn">{{Cite web |title=What Is Automated Signature Verification? |url=https://sqnbankingsystems.com/blog/what-is-automated-signature-verification/ |access-date=2020-08-07 |website=SQN Banking Systems |language=en-US}}</ref><ref name="mayhew">{{Cite web |last=Mayhew |first=Stephen |date=2012-05-14 |title=Banks Are Now Embracing The Newer And Tougher Signature Verification System |url=https://www.biometricupdate.com/201205/banks-are-now-embracing-the-newer-and-tougher-signature-verification-system |access-date=2020-08-07 |website=Biometric Update |language=en-US}}</ref> The highest error rates in signature verification are found with lay people, higher than for computers, which in turn make more errors than experts.<ref name="comp-methods">{{Cite report |title=Computational Methods for Handwritten Questioned Document Examination |url=https://nij.ojp.gov/library/publications/computational-methods-handwritten-questioned-document-examination |publisher=[[National Institute of Justice]] |date=December 2010 |last1=Srihari |first1=Sangur }}</ref>

There have been concerns that signature reviews improperly reject ballots from young and minority voters at higher rates than others, with no or limited ability of voters to appeal the rejection.<ref name="aclu">{{Cite web |title=Vote-By-Mail Ballots Cast in Florida |url=https://www.aclufl.org/sites/default/files/aclufl_-_vote_by_mail_-_report.pdf |last=Smith |first=Daniel |date=2018-09-18 |website=ACLU-Florida |access-date=2020-06-01 |archive-date=2020-12-02 |archive-url=https://web.archive.org/web/20201202043232/https://www.aclufl.org/sites/default/files/aclufl_-_vote_by_mail_-_report.pdf |url-status=dead }}</ref>
<ref name="who">{{Cite news |last=Wilkie |first=Jordan |date=2018-10-12 |title=Exclusive: High Rate of Absentee Ballot Rejection Reeks of Voter Suppression |work=Who What Why |url=https://whowhatwhy.org/2018/10/12/exclusive-high-rate-of-absentee-ballot-rejection-reeks-of-voter-suppression/ |access-date=2020-06-18}}</ref> When errors are made with bank checks, the payer can ask the bank for corrections.

In 2018, a fifth of adults in the United Kingdom said they sign so rarely they have no consistent signature, including 21% of people 18-24 and 16% of people over age 55. 55% of UK adults said they rarely sign anything.<ref name="spy">{{Cite web |date=2018 |title=Sign Of The Times - One In Five Adults Don't Have Their Own Signature |url=https://www.onlinespyshop.co.uk/blog/sign-of-the-times-one-in-five-adults-dont-have-their-own-signature/ |access-date=2021-03-19 |website=OSS Technology |language=en}}</ref>

Researchers have published error rates for computerized signature verification. They compare different systems on a common database of true and false signatures. The best system falsely rejects 10% of true signatures, while it accepts 10% of forgeries. Another system has error rates on both of 14%, and the third-best has error rates of 17%.<ref name="hafe-lr">These systems handle scanned ("offline") signatures from multiple people ("WI, writer-independent"). {{Cite book |last1=Hafemann |first1=Luiz G.| first2=Robert|last2= Sabourin | first3=Luiz S. |last3=Oliveira |title=2017 Seventh International Conference on Image Processing Theory, Tools and Applications (IPTA) |date=2017-10-16 |chapter=Offline handwritten signature verification — Literature review |publisher=IEEE|pages=1–8 |doi=10.1109/IPTA.2017.8310112 |arxiv=1507.07909 |isbn=978-1-5386-1842-4 |s2cid=206932295 }}</ref><ref name="bibi">{{Cite journal |last1=Bibi |first1=Kiran |last2=Naz |first2=Saeeda |last3=Rehman |first3=Arshia |date=2020-01-01 |title=Biometric signature authentication using machine learning techniques: Current trends, challenges and opportunities |url=https://doi.org/10.1007/s11042-019-08022-0 |journal=Multimedia Tools and Applications |language=en |volume=79 |issue=1 |pages=289–340 |doi=10.1007/s11042-019-08022-0 |s2cid=199576552 |issn=1573-7721|url-access=subscription }}</ref> It is possible to be less stringent and reject fewer true signatures, at the cost of also rejecting fewer forgeries.<ref name="igarza">{{Cite conference |last1=Igarza |first1=Juan |last2=Goirizelaia |author-link2=Iñaki Goirizelaia |first2=Iñaki |last3=Espinosa |first3=Koldo |last4=Hernáez |first4=Inmaculada |last5=Méndez |first5=Raúl |last6=Sanchez |first6=Jon |date=2003-11-26 |title=Online Handwritten Signature Verification Using Hidden Markov Models |url=https://www.researchgate.net/publication/220842960 |conference=CIARP 2003 |volume=2905 |pages=391–399 |doi=10.1007/978-3-540-24586-5_48|doi-access=free }}</ref> Computer algorithms:<blockquote>look for a certain number of points of similarity between the compared signatures ... a wide range of algorithms and standards, each particular to that machine's manufacturer, are used to verify signatures. In addition, counties have discretion in managing the settings and implementing manufacturers' guidelines ... there are no statewide standards for automatic signature verification ... most counties do not have a publicly available, written explanation of the signature verification criteria and processes they use.<ref name="stan">{{Cite web |title=Signature Verification and Mail Ballots: Guaranteeing Access While Preserving Integrity |url= https://www-cdn.law.stanford.edu/wp-content/uploads/2020/04/FINAL-Signature-Verification-Report-4-15-20.pdf |date=2020-04-15 |publisher=Stanford University |access-date=2020-06-01}}</ref></blockquote>

In an experiment, experts rejected 5% of true signatures and 71% of forgeries. They were doubtful about another 57% of true signatures and 27% of forgeries. If computer verification is adjusted to reflect what experts are sure about, it will wrongly reject 5% of true signatures and wrongly accept 29% of forgeries. If computers were adjusted more strictly, rejecting all signatures which experts have doubts about, the computers would set aside 62% of true signatures, and still wrongly accept 2% of forgeries. Lay people made more mistakes and were doubtful less often, though the study does not report whether their mistakes were to accept more forgeries or reject more true signatures.<ref name="sita"/>

Voters with short names are at a disadvantage, since experts make more mistakes on signatures with fewer "turning points and intersections." Participants in this study had 10 true signatures to compare to, which is more than most postal ballot verifications have.<ref name="sita">{{Cite journal |last1=Sita |first1=Jodi |last2=Found |first2=Bryan |last3=Rogers |first3=Douglas K. |date=September 2002 |title=Forensic Handwriting Examiners' Expertise for Signature Comparison |url=https://www.academia.edu/1361670 |journal=[[Journal of Forensic Sciences]] |language=en |volume=47 |issue=5 |pages=1117–1124 |doi=10.1520/JFS15521J |pmid=12353558 |issn=0022-1198}}</ref> A more recent study for the US Department of Justice confirms the probabilistic nature of signature verification, though it does not provide numbers.<ref name="comp-methods" />

===Online usage===
{{main|Signature block}}
{{see also|Real-name system}}
In [[e-mail]] and [[newsgroup]] usage, another type of signature exists which is independent of one's language. Users can set one or more lines of custom text known as a [[signature block]] to be automatically appended to their messages. This text usually includes a name, contact information, and sometimes quotations and [[ASCII art]]. A shortened form of a signature block, only including one's name, often with some distinguishing prefix, can be used to simply indicate the end of a [[posting style|post]] or response. Some web sites also allow graphics to be used. Note, however, that this type of signature is not related to [[electronic signature]]s or [[digital signature]]s, which are more technical in nature and not directly understandable by humans.

===Reusing signature pages===
For guidance applicable in [[England and Wales]] on the use of pre-signed signature pages being subsequently attached to documents to effect a "virtual" signing, see [[Law of Property (Miscellaneous Provisions) Act 1989#Validity of execution under Mercury]].

==Art==
[[File:Vermeer autograph.svg|thumb|[[Vermeer]]'s signature]]
The '''signature''' on a painting or other work of art is an important factor in assessing [[provenance]]. Fake signatures are sometimes added to enhance the value of a painting, or are added to a fake painting to support its authenticity. A notorious case was the signature of [[Johannes Vermeer]] on the fake "Supper at Emmaus" made by the art forger [[Han van Meegeren]]. However, the fact that painters' signatures often vary over time (particularly in the modern and contemporary periods) might complicate the issue. The signatures of some painters take on an artistic form that may be of less value in determining forgeries.
If a painting is [[abstract painting|abstract]] or [[ambiguous figure|ambiguous]], the signature may be the only clue to determine which side is up.

==Copyright==
Under British law, the appearance of signatures (not the names themselves) may be protected under [[Copyright law of the United Kingdom|copyright law]].<ref name=Spilsbury>{{cite book | title=Media Law | last=Spilsbury | first=Sallie | publisher=Cavendish Publishing | year=2000 | isbn=978-1-85941-530-6 | page=[https://books.google.com/books?id=X2qyT3Y7IpEC&pg=PA439 p. 439]| quote=An individual's signature may be protected under law as an artistic work. If so, the unauthorised reproduction of the signature will infringe copyright. The name itself will ''not'' be protected by copyright; it is the ''appearance'' of the signature which is protected.}}</ref>

Under [[Copyright law of the United States|United States copyright law]], "titles, names [I c...]; mere variations of typographic ornamentation, lettering, or coloring" are not eligible for copyright;<ref>"[http://www.copyright.gov/circs/circ1.pdf Copyright Basics] {{webarchive|url=https://web.archive.org/web/20110305163016/http://www.copyright.gov/circs/circ1.pdf |date=2011-03-05 }}", [[United States Copyright Office]]. Retrieved 15 March 2011.</ref> however, the appearance of signatures (not the names themselves) may be protected under copyright law.<ref name=Spilsbury />

==Uniform Commercial Code==

[[Uniform Commercial Code]] §1-201(37) of the United States generally defines '''signed''' as "using any symbol executed or adopted with present intention to adopt or accept a writing". The Uniform Commercial Code §3-401(b) for [[negotiable instruments]] states "A signature may be made (i) manually or by means of a device or machine, and (ii) by the use of any name, including a [[Trademark|trade]] or assumed name, or by a word, mark, or symbol executed or adopted by a person with present intention to authenticate a writing."

==See also==
{{Spoken Wikipedia|Signature.ogg|date=2006-05-21}}
*[[Autograph club]]
*''[[Autograph Collector Magazine]]''
*[[Biometric signature]] as form of the [[electronic signature]]
*[[Builder's signature]]
*[[Initials]]
*[[:Category:Images of signatures|Images of signatures]]
*''[[manu propria]]'' (''m.p.'')
*[[Memorial to the 56 Signers of the Declaration of Independence]], includes depicted signatures  
*[[Monogram]]
*[[Pawtograph]], an animal's paw print
* [[Round-robin (document)]], a signed document where the signatures are arranged in a circle
*[[Royal sign-manual]]
*[[Shakespeare's handwriting]]
*[[Signum manus]]
*[[Tughra]]
*[[Huaya]]

==References==
{{Reflist}}

==External links==
{{commons category|Signatures}}
{{Wikidata property |P109}}
{{Wiktionary}}
*[https://www.npr.org/blogs/money/2014