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Open O

Open o (majuscule: Ɔ; minuscule: ɔ) is a letter in the extended Latin alphabet, typographically formed as a turned lowercase c, and is primarily used in the International Phonetic Alphabet (IPA) to denote the open-mid back rounded vowel sound /ɔ/.^[1] The symbol's lowercase form, ɔ, is encoded in Unicode as U+0254 in the IPA Extensions block, while its uppercase counterpart, Ɔ, is U+0186 in the Latin Extended-B block. In phonetics, the open o represents a vowel articulated with the tongue positioned in the back of the mouth, at an open-mid height, and with rounded lips, distinguishing it from the closer /o/ sound.^[2] This phoneme appears in numerous languages worldwide, including dialects of English without the cot–caught merger, where it occurs in words such as "thought," "law," and "caught," such as in Received Pronunciation and northeastern and southern U.S. varieties.^[3] It also features prominently in languages like French (as in bonne /bɔn/), German, Italian, and Portuguese.^[4] Beyond phonetics, open o is employed in the orthographies of various languages, especially those adopting the African reference alphabet, such as Adangme, Dagbani, and Ewe in West Africa. Historically, it has appeared in transcriptions for other sounds, including the alveolar ejective affricate /tsʼ/ in colonial Yucatec Maya orthography,^[5] and it continues to be used in modern Latin-based scripts for African languages to accurately represent distinct vowel qualities. The letter's design facilitates precise linguistic documentation and supports the transcription of sounds not adequately covered by standard Latin vowels.

Overview and Phonetics

Phonetic Symbolism

The open O, represented by the symbol [ɔ] in the International Phonetic Alphabet (IPA), denotes the open-mid back rounded vowel. This sound is characterized by a tongue position at lowered mid-height in the back of the oral cavity, with the tongue body retracted toward the soft palate, accompanied by protrusion and rounding of the lips, and typically produced with modal voice through vibration of the vocal folds.^[6] The symbol [ɔ] originated in the phonetic systems developed by Alexander John Ellis, who introduced a precursor form—an "O with flourish"—in his 1848 article on the Phonetic Alphabet published in The Phonotypic Journal, as part of efforts to create a universal transcription for sounds across languages. It was subsequently adopted and standardized in the IPA following the association's founding in 1886, with the first official IPA chart appearing in 1888.^[7]^[8] In phonetic transcription, [ɔ] captures vowel qualities in various languages; for instance, it represents the nucleus in the English word "thought" [θɔːt] as spoken in Received Pronunciation, and in French, it appears in words like "or" [ɔʁ] meaning "gold." These transcriptions highlight its role in distinguishing lexical items based on vowel openness and rounding.^[3]^[9] Acoustically, the open-mid back rounded vowel [ɔ] exhibits characteristic formant frequencies that reflect its articulatory configuration, with the first formant (F1) typically ranging from 500 to 600 Hz—indicative of its mid-to-open height—and the second formant (F2) from 800 to 1000 Hz, signaling the retracted tongue position and lip rounding. These values, derived from measurements of adult male speakers in Canadian English, underscore how [ɔ] occupies a distinct position in the vowel space relative to closer back vowels like .^[10]

Visual Description

The Latin small letter open o (ɔ) is graphically structured as a turned lowercase "c", formed by rotating the standard "c" glyph 180 degrees to create an incomplete circular shape with the opening facing right. This design results in a prominent counter space, visually distinguishing it from the closed loop of a standard "o" while maintaining a rounded, organic form. The uppercase counterpart, Ɔ (U+0186), adopts a similar mirrored or inverted structure based on a turned uppercase "C", though it is employed less commonly in phonetic transcription.^[11] In typographic design, the open o glyph adheres to proportional standards typical of lowercase letters, with its height aligned to that of the "o" and a width roughly 0.6-0.8 em to accommodate the open counter, ensuring balanced integration in text flows; the stroke weight remains consistent with surrounding characters for optical evenness.^[1] Variations across typefaces reflect broader stylistic principles: in serif designs such as those in the Stone Phonetic family, the curve exhibits subtle angular transitions at the endpoints for enhanced readability in printed matter, whereas sans-serif renderings, like those in Noto Sans, favor smoother, continuous arcs without decorative flourishes.^[12] These adaptations preserve the glyph's core openness while adapting to the typeface's overall aesthetic and legibility requirements.^[13]

Historical Development

Origins in Phonetic Transcription

The open O symbol (ɔ), also known as the turned c or open o, was introduced by British phonetician Alexander John Ellis in 1848 in an article in The Phonotypic Journal, as part of his early work on phonetic transcription systems, including the later-developed palaeotype transcription system, a comprehensive phonetic alphabet designed to represent English sounds using modified Roman letters and diacritics. This symbol specifically denoted the open-mid back rounded vowel, as heard in words such as "law," allowing for precise notation of dialectal variations in English pronunciation.^[14] In palaeotype, the open O played a crucial role in distinguishing the open-mid back rounded vowel [ɔ] from the close-mid and open [ɒ], enabling detailed transcription of vowel qualities in Ellis's extensive surveys of English dialects. The symbol's design—a rotated lowercase c—reflected Ellis's principle of deriving phonetic characters from familiar letter forms while adapting them for auditory accuracy, facilitating both broad and narrow transcriptions. The open O exemplified Ellis's effort to create a universal system applicable to any language, influencing subsequent phonetic notations by providing a dedicated marker for this vowel phoneme. The symbol gained further traction through the work of Henry Sweet in the 1880s, who incorporated a similar turned c in his romic notation system, building on Ellis's palaeotype to simplify phonetic representation for practical use in language teaching and dialectology. Sweet's adaptations emphasized the open O's utility in broad transcriptions, as seen in his Handbook of Phonetics (1877, revised 1890), where it helped differentiate vowel heights in English and other languages. This evolution bridged Ellis's detailed system to more accessible notations.^[15] A pivotal development occurred in 1888 when the Phonetic Teachers' Association—precursor to the International Phonetic Association—adopted the open O in its prototype alphabet, integrating it into an international standard for phonetic transcription based partly on Ellis's and Sweet's contributions. The symbol appeared in the first official IPA chart in 1897 and remained unchanged in subsequent revisions, confirming its standardization. By 1900, refinements to the International Phonetic Alphabet (IPA) solidified the symbol's form and placement on vowel charts, ensuring its role in distinguishing [ɔ] amid ongoing debates on vowel classification during the association's early congresses.

Evolution and Standardization

The open O symbol, representing the open-mid back rounded vowel [ɔ], underwent significant refinements in the 20th century as part of broader efforts to enhance clarity and precision in the International Phonetic Alphabet (IPA). The 1989 Kiel Convention marked a pivotal revision, reformulating the IPA's principles to incorporate distinctive feature theory and standardizing symbol usage for better international consistency, including distinctions among back vowels like [ɔ] and the more open [ɒ].^[16] This adjustment emphasized articulatory categories to separate open-mid from near-open realizations, facilitating more accurate phonetic transcription across languages.^[16] Subsequent updates further refined diacritic applications for variants of [ɔ]. The 1989 revisions, detailed in subsequent IPA publications, introduced or clarified modifiers such as the lowering diacritic [ɔ̞] to denote lax or lowered open-mid qualities, allowing phoneticians to capture subtle allophonic differences without introducing new base symbols.^[16] The International Phonetic Association's 1999 handbook, building on 1993 chart refinements, specified guidelines for glyph consistency, ensuring the open O's form—a turned lowercase c—remained uniform in printed and handwritten forms to support reliable cross-linguistic comparisons.^[16] The 2020 IPA chart revision maintained this symbol's placement in the vowel quadrilateral while updating typographic recommendations for digital rendering and fieldwork notation.^[6] A key milestone in applying the open O to practical orthographies occurred with the International African Institute's 1930 Practical Orthography of African Languages, which recommended the use of ɔ, influenced by IPA conventions, to represent prevalent open-mid vowels, transitioning phonetic accuracy into everyday writing systems for various African languages.^[17] These efforts highlighted the symbol's role in harmonizing phonetic notation with regional literacy initiatives, fostering broader adoption in educational and publishing contexts.^[17]

Linguistic Usage

In African Languages

The open O (ɔ) is employed in the orthographies of many African languages, particularly within the Bantu and Niger-Congo families, to denote the open-mid back rounded vowel sound. This character facilitates precise representation of phonetic distinctions essential for accurate pronunciation and literacy in these tongues. Its adoption stems from efforts to harmonize Latin-based scripts across the continent, ensuring consistency in transcribing complex vowel inventories.^[18] Standardization of ɔ occurred through the 1978 African Reference Alphabet (ARA), formulated at the UNESCO-sponsored workshop in Niamey, Niger, under the auspices of the Organization of African Unity. The ARA advocated ɔ for open-mid vowels, replacing varied ad hoc symbols like accented o or diaeresis combinations in prior systems, and applying the "one sound, one symbol" principle to promote literacy in Niger-Congo and other language groups. This framework influenced orthographies in West and Central Africa, including those of approximately 60 national languages in Côte d'Ivoire.^[19] The historical integration of ɔ traces back to early 20th-century missionary efforts and linguistic standardization initiatives. Introduced in phonetic transcription scripts during the 1920s for languages like variants of Swahili and other Bantu dialects, it gained formal endorsement in the 1930 Practical Orthography of African Languages by the International Institute of African Languages and Cultures, which recommended ɔ to differentiate open from close o sounds. UNESCO bolstered this in the 1960s through literacy programs, notably the 1966 Bamako workshop, which laid groundwork for the Niamey recommendations and extended ɔ's use in West African orthographies for languages such as Manding and Fulfulde.^[17] Representative examples illustrate ɔ's practical application. In Lingala, a Bantu language spoken in the Democratic Republic of the Congo, ɔ distinguishes the open vowel in words like ndɔbɔ (fishhook), contrasting with ndobo (mousetrap) to avoid ambiguity. In Bambara, a Manding language of Mali, ɔ represents the open o in terms like bɔgɔ (arm), separating it from the closed o in bogo (to bury). For Zulu, while standard orthography merges the sounds into o, some dialectal or phonetic representations in academic and missionary contexts employ ɔ for precise [ɔ] sounds in southern Bantu variants. In Yoruba, a Niger-Congo language of Nigeria, the open [ɔ] is typically marked as ọ, but historical IPA-influenced scripts occasionally used ɔ before standardization favored the dotted form for distinction from .^[20]^[21]

Other Orthographic and Dialectal Applications

In older Danish orthography, prior to the 1948 spelling reform, the open O combined with a colon (ɔ:) served as the "forklaringstegn" or explanatory symbol, equivalent to "that is" (id est) or "namely," appearing in printed texts as early as the 19th century.^[22] This usage, rooted in medieval scribal traditions, persisted in Danish and Norwegian publications, such as Rasmus Rask's 1826 grammatical work and Knud Knudsen's 1881 linguistic treatise, to introduce clarifications or examples without full phrases.^[22] During the colonial period in the Yucatán Peninsula (16th to 19th centuries), early orthographic conventions for Yucatec Maya employed the open O (often as a lowercase reversed C, ɔ) to represent the alveolar ejective affricate /t͡sʼ/, a glottalized consonant sound distinct from standard Latin letters.^[18] This symbol appeared in Spanish missionary grammars and indigenous-authored documents, such as those compiled in the 18th century, before modern revisions shifted to digraphs like tzʼ for clarity in phonetic transcription. By the early 20th century, as standardized Latin-based systems emerged, the open O fell out of common use in favor of more accessible notations, though it lingered in historical linguistic records. In English dialectology, the open O features prominently in phonetic notations to capture regional vowel variations, such as the open-mid back rounded vowel [ɔː] in Received Pronunciation for words like "horse" or "thought," distinguishing it from broader /ɑː/ in other dialects. This application extends to broader studies of British English dialects, where narrow transcription using the open O highlights subtle shifts, as documented in mid-20th-century surveys of urban and rural speech patterns.

Character Encoding and Typography

Unicode Representation

The lowercase form of the open o character is encoded in Unicode as U+0254, named LATIN SMALL LETTER OPEN O, and resides in the IPA Extensions block (U+0250–U+02AF).^[23] This code point was introduced in Unicode version 1.1, released in 1993. Its general category is Letter, Lowercase (Ll), with a bidirectional class of Left-to-Right (L) and no canonical decomposition.^[23] The uppercase counterpart is encoded as U+0186, named LATIN CAPITAL LETTER OPEN O, and is located in the Latin Extended-B block (U+0180–U+024F).^[24] It shares the bidirectional class of Left-to-Right (L) and has no decomposition, with a general category of Letter, Uppercase (Lu).^[24] The lowercase form maps to U+0254 via case folding and normalization processes.^[24] In terms of normalization, both code points remain unchanged under Unicode Normalization Forms NFC and NFD due to the absence of decomposition mappings. For collation and sorting, open o is frequently handled as a phonetic variant of the standard Latin letter "o" in linguistic algorithms, such as those tailored for phonetic transcription systems, to maintain alphabetical proximity in specialized indexes.^[25] This treatment aligns with the Unicode Collation Algorithm's tailoring options for extended Latin scripts in academic and linguistic applications.^[25]

Typographic Variants and Compatibility

The open O (ɔ) exhibits typographic variants that distinguish its rendering in different contexts, such as the "turned c" style often employed in handwriting for fluidity, compared to the more standardized "open loop" form in printed typography. Font designers typically avoid automatic ligatures involving the open O with adjacent letters to prevent visual distortions, relying instead on kerning pairs for optimal spacing in digital layouts. Modern fonts provide robust support for the open O glyph, including families like Noto Sans and the SIL International's Charis SIL, which cover IPA extensions.^[12] In contrast, pre-2000 Windows systems featured partial support in standard fonts such as Arial or Times New Roman, often necessitating fallback mechanisms to specialized IPA fonts for proper rendering of ɔ.^[12] HTML entities facilitate its use in web content, with ɔ (decimal) or ɔ (hexadecimal) for the lowercase form and Ɔ (decimal) or Ɔ (hexadecimal) for the uppercase Ɔ.^[26] In early PDF versions and viewers prior to the mid-2000s, embedding of the open O often posed compatibility challenges due to limited font and IPA support, leading to substitution or omission glyphs. Browser compatibility for the open O has evolved since Internet Explorer 5.5 in 2000, which introduced initial Unicode rendering for extended Latin characters including U+0254. Mobile platforms saw significant improvements with iOS 4 in 2010, enhancing IPA symbol display through updated system fonts, and Android 4.0 in 2011, which better handled phonetic glyphs via improved fallback chains. As of 2025, open O enjoys full support in all major operating systems, web browsers, and PDF viewers, with comprehensive coverage in system fonts like those in Windows 11, macOS, and Linux distributions.^[27]

Descendants in Extended Latin Scripts

The open o (ɔ) serves as the base for its uppercase counterpart, the Latin capital letter open O (Ɔ, U+0186), which is employed in the orthographies of numerous African languages as part of extended Latin scripts. This form represents the open-mid back rounded vowel and was incorporated into the African Reference Alphabet (ARA) of 1978 to standardize phonetic representations across diverse linguistic families, including Niger-Congo and Nilo-Saharan languages such as Akan, Ewe, and Dinka. The ARA's inclusion of Ɔ/ɔ facilitated consistent transcription in colonial and post-colonial contexts, influencing subsequent national standards like the Pan-Nigerian Alphabet standardized in the 1980s by Nigeria's National Language Centre, where it supports vowel distinctions in various indigenous languages.^[18] A direct derivative is the Latin letter open O with hook (ʘ, U+0298), used to denote the bilabial click consonant in Khoisan languages of southern Africa, particularly in the Tuu family such as !Xóõ and Nǀuu. This symbol, first documented in 19th-century transcriptions, combines the open o shape with a rightward hook to visually and phonetically evoke the lip-smacking ingressive airstream mechanism unique to these languages. Its adoption stems from extensions to the International Phonetic Alphabet (IPA) for non-pulmonic consonants, ensuring precise representation in linguistic documentation of endangered Khoisan varieties.^[6] In the extended IPA, modifications to the open o employ combining diacritics to indicate articulatory variations, such as the raised open o [ɔ̝] (using U+031D combining up tack) for a higher vowel position or the lowered open o [ɔ̞] (using U+031E combining down tack) for a more open realization. These are applied in phonetic analyses of disordered speech or dialectal variations, extending the base symbol's utility beyond standard vowels.^[28] ARA-inspired extensions include tone-marked variants like open o with acute (ɔ́), prevalent in tone languages such as Ewe, where it distinguishes high-tone open-mid vowels in Gbe family orthographies. This form evolved from IPA phonetic bases adapted in the 1978 ARA to accommodate tonal systems in West African scripts, promoting readability in printed materials and education.^[29] The progression from IPA origins to ARA standardization underscores the open o's role in bridging phonetic precision with practical orthographic needs in extended Latin systems.

Visually Similar Letters

The Greek letter theta (Θ/θ, U+0398/U+03B8) features a closed circular form intersected by a horizontal bar, serving in the International Phonetic Alphabet to denote the voiceless dental fricative [θ]. This symbol originates from ancient Greek, where it initially represented an aspirated voiceless dental plosive /tʰ/, shifting to the fricative value in later historical Greek and adopting its modern phonetic role in the IPA since the late 19th century.^[30]^[31] The Cyrillic letter ef (Ф/ф, U+0424/U+0444), derived from the Greek phi (Φ/φ), consists of a full circular loop with a vertical bar extending downward on the right side, mirroring a reversed form of phi but lacking any phonetic connection to the open-mid back rounded vowel [ɔ]. It represents the voiceless labiodental fricative /f/ in Slavic languages and related scripts, with no overlap in usage or sound value relative to the open O in phonetic notation. In mathematical contexts, the empty set symbol ∅ (U+2205) appears as a slashed or partially struck-through circle, introduced by André Weil in 1939 and popularized through the Bourbaki group's works, becoming a standard in set theory by the mid-20th century to denote a set with no elements. This differs from the open O through its diagonal slash across a closed form, rather than an open gap, ensuring distinction in typographic rendering.^[32] Key distinctions among these characters include the open O's (U+0254) inherent asymmetry, characterized by a right-facing gap in its turned "c" shape representing the open-mid back rounded vowel [ɔ], in contrast to the symmetric closed structures of theta and ef, or the slashed symmetry of the empty set. In Unicode collation under the default algorithm, Greek theta sorts after basic Latin letters but before many extended IPA symbols, potentially placing it near digraphs like "th" in tailored linguistic orderings where phonetic equivalence influences grouping, though standard rules prioritize script blocks to avoid unintended merges.^[23]^[25]

References

[1]
LATIN SMALL LETTER OPEN O - ScriptSource
Open O [306]. Upper Case: 0186 - LATIN CAPITAL LETTER OPEN O. IPA Description: Open-mid back rounded vowel. Phonetic Symbol Guide Equivalent: Open O [PSG2.143] ...
[2]
Open-mid back rounded vowel [ɔ] - Teflpedia
Feb 5, 2025 · In the International Phonetic Alphabet, the open-mid back rounded vowel is represented by a lowercase open o symbol, ⟨ɔ⟩. Its IPA number is 306.
[3]
IPA symbol: [ɔ]
Many dialects of English have another vowel, which is represented by the "open o" symbol, [ɔ]. Most dialects spoken in Canada and in the central and western US
[4]
O - French Pronunciation
[ɔ] is called the open o sound.* Phonetic symbol: [ɔ]. It's similar to the short u sound as in the English word "son." When O is followed by any consonant ...
[5]
Full IPA Chart | International Phonetic Association
### Summary of Symbol [ɔ] from IPA Chart
[6]
https://www.internationalphoneticassociation.org/content/full-ipa-chart
[7]
History of the IPA | International Phonetic Association
B. 1958. For reproductions of some earlier IPA charts, including the first one in 1888, see MacMahon, M K C, 'Phonetic notation', in Daniels, P T & Bright, W ( ...
[8]
French IPA - Vowels - Lawless French Pronunciation
Voyelles en IPA ; [ɔ], O · gazole – horrifié ; [u], OU · courgette – nous ; [y], U · Û, tu – carburant · bûcher ; Nasal vowels.Missing: English | Show results with:English
[9]
Formants - Acoustic Phonetics
We can place each vowel on a graph, where the horizontal dimension represents the frequency of the first formant (F1) and the vertical dimension represents the ...
[10]
U+0254 LATIN SMALL LETTER OPEN O: ɔ – Unicode
### Summary of Visual Form, Design, or Typography of Open O (ɔ)
[11]
IPA Fonts | International Phonetic Association
LaserIPA fonts (IPARoman, IPAKiel, IPAKielSeven and IPAExtras) contain all the necessary symbols from the IPA chart and from the list of numbers and codings.
[12]
None
Summary of each segment:
[13]
The Essentials of Phonetics
- **Book Title**: The Essentials of Phonetics
[14]
A handbook of phonetics : Sweet, Henry, 1845-1912 - Internet Archive
Jun 7, 2008 · A Handbook of Phonetics. Book digitized by Google from the library of Harvard University and uploaded to the Internet Archive by user tpb.
[15]
[PDF] Handbook_of_the_IPA.pdf
The Handbook presents the basics of phonetic analysis so that the principles underlying the Alphabet can be readily understood, and exemplifies the use of each ...
[16]
Field, Ears, and Laboratory: Training Language Scholars, 1920–1940
Sep 23, 2021 · The goal of the fieldwork was not to learn to speak the language, but instead to record it and analyze it on paper. Second, the recording ...
[17]
Latin Extended-B - Unicode
African languages. •, lowercase is 0254 ɔ. →, 1D10 ᴐ latin letter small capital open o. →, 2183 Ↄ roman numeral reversed one hundred. ↓, 0254 ɔ latin small ...
[18]
Niamey 1978 report
Extract of the final report on the Regional seminar on the harmonization and standardization of the alphabets of the languages of Ghana, Togo, Upper Volta, ...
[19]
IIALC 1930, Practical Orthography of African Languages
Close and open e and o (i.e. e and ɛ, o and ɔ) distinguish words in French, most West African languages, Chwana,. PRACTICAL ORTHOGRAPHY OF AFRICAN LANGUAGES 17.Missing: 1949 | Show results with:1949
[20]
Lingala/Keyboard - LING073 - Swarthmore College
Feb 9, 2017 · Lingala contains 35 letters and digraphs. It has seven vowels, including 'ɛ' and 'ɔ' in addition to the five vowels used in English. Of the ...
[21]
Ɔ vs O (AKA "closed O" vs "open O") in Bambara - An ka taa
Aug 27, 2024 · O (which is often referred to as “closed O”) and Ɔ (“open O”) are letters that represent O-sounds, but they are distinct. To help people for ...
[22]
None
### Properties of U+0254 LATIN SMALL LETTER OPEN O
[23]
None
**Properties of U+0186 LATIN CAPITAL LETTER OPEN O:**
[24]
https://www.unicode.org/charts/PDF/U0180.pdf
[25]
ISO 9:1995 - Information and documentation
Establishes a system for the transliteration into Latin characters of Cyrillic characters constituting the alphabets of Slavic and non-Slavic languages.Missing: ɔ | Show results with:ɔ
[26]
Unicode Character 'LATIN SMALL LETTER OPEN O' (U+0254)
OPEN O, LATIN SMALL LETTER O, LATIN SMALL LETTER OPEN. Upper case, U+0186. Title case, U+0186. Comments, typographically a turned c lower-mid back rounded vowel
[27]
[PDF] CLICKS IN XHOSA AND NAMA: A COMPARATIVE ANALYSIS
Jan 12, 2010 · Neither Nama nor. Xhosa have a bilabial click; only the Southern Khoisan languages, such as |Xam and !Xóõ do (Ladefoged & Maddieson 1996:249) ...
[28]
[PDF] UNITIPA Symbol list of the International Phonetic Alphabet (revised ...
Name: VOICELESS BILABIAL PLOSIVE. IPA name: Lower-case P. IPA number: 101. Unicode name: LATIN SMALL LETTER P. Unicode range: Basic Latin. Hex value:.Missing: revisions handbook glyph consistency
[29]
[PDF] Basic Ewe for foreign students
o a closed o, like in Italian rotto ɔ an open o, like in hot p as in palm r pronounced with the tip of the tongue (like in Italian rosso) s as in silver t ...
[30]
[PDF] On the 1978 version of the African Reference Alphabet - Unicode
Oct 9, 2021 · The African Reference Alphabet (ARA) was a project originating from UNESCO, to create a uniform system, to faithfully transcribe a wide variety ...
[31]
[PDF] Greek and Coptic - The Unicode Standard, Version 17.0
0398 Θ GREEK CAPITAL LETTER THETA. 0399. Ι GREEK CAPITAL LETTER IOTA. = iota ... → 0180 ƀ latin small letter b with stroke. → A7B5 ꞵ latin small letter ...
[32]
IPA symbol: [θ]
This symbol was borrowed from the Greek alphabet and is called by the name of the Greek letter: theta [ˈθetə]. If you're having problems hearing the ...
[33]
How did mathematicians notate the empty set before $\varnothing
Jul 8, 2015 · The modern symbol ∅ or ∅ was indeed introduced in 1939 by Andre Weil, and gained wide acceptance after its use in the Bourbaki volumes.mathematics - Who is the first to use $\{\,\}$ to denote the empty set?Origin of Q for the set of rational numbers?More results from hsm.stackexchange.com