Home U+2200 to U+22FF Mathematical Operators
Glyph for U+2205
Source: Noto Sans Math

U+2205 Empty Set

U+2205 was added in Unicode version 1.1 in 1993. It belongs to the block U+2200 to U+22FF Mathematical Operators in the U+0000 to U+FFFF Basic Multilingual Plane.

This character is a Math Symbol and is commonly used, that is, in no specific script. The character is also known as null set.

The glyph is not a composition. It has no designated width in East Asian texts. In bidirectional text it acts as Other Neutral. When changing direction it is not mirrored. The word that U+2205 forms with similar adjacent characters prevents a line break inside it. The glyph can be confused with one other glyph.

The CLDR project calls this character “empty set” for use in screen reading software. It assigns these additional labels, e.g. for search in emoji pickers: empty, mathematics, operator, set.

The Wikipedia has the following information about this codepoint:

In mathematics, the empty set or void set is the unique set having no elements; its size or cardinality (count of elements in a set) is zero. Some axiomatic set theories ensure that the empty set exists by including an axiom of empty set, while in other theories, its existence can be deduced. Many possible properties of sets are vacuously true for the empty set.

Any set other than the empty set is called non-empty.

In some textbooks and popularizations, the empty set is referred to as the "null set". However, null set is a distinct notion within the context of measure theory, in which it describes a set of measure zero (which is not necessarily empty).

Representations

System Representation
Nº 8709
UTF-8 E2 88 85
UTF-16 22 05
UTF-32 00 00 22 05
URL-Quoted %E2%88%85
HTML hex reference ∅
Wrong windows-1252 Mojibake ∅
HTML named entity ∅
HTML named entity ∅
HTML named entity ∅
HTML named entity ∅
alias null set
Encoding: EUC_JIS_2004 (hex bytes) A2 C7
Encoding: EUC_JISX0213 (hex bytes) A2 C7
Encoding: GB18030 (hex bytes) 81 36 D2 31
Encoding: ISO2022_JP_2004 (hex bytes) 1B 24 28 51 22 47 1B 28 42
Encoding: ISO2022_JP_3 (hex bytes) 1B 24 28 4F 22 47 1B 28 42
Encoding: SHIFT_JIS_2004 (hex bytes) 81 C5
Encoding: SHIFT_JISX0213 (hex bytes) 81 C5
LATEX \varnothing
Adobe Glyph List emptyset
digraph /0

Related Characters

Confusables

Elsewhere

Complete Record

Property Value
Age (age) 1.1 (1993)
Unicode Name (na) EMPTY SET
Unicode 1 Name (na1) —
Block (blk) Mathematical Operators
General Category (gc) Math Symbol
Script (sc) Common
Bidirectional Category (bc) Other Neutral
Combining Class (ccc) Not Reordered
Decomposition Type (dt) none
Decomposition Mapping (dm) Glyph for U+2205 Empty Set
Lowercase (Lower) ✘
Simple Lowercase Mapping (slc) Glyph for U+2205 Empty Set
Lowercase Mapping (lc) Glyph for U+2205 Empty Set
Uppercase (Upper) ✘
Simple Uppercase Mapping (suc) Glyph for U+2205 Empty Set
Uppercase Mapping (uc) Glyph for U+2205 Empty Set
Simple Titlecase Mapping (stc) Glyph for U+2205 Empty Set
Titlecase Mapping (tc) Glyph for U+2205 Empty Set
Case Folding (cf) Glyph for U+2205 Empty Set
ASCII Hex Digit (AHex) ✘
Alphabetic (Alpha) ✘
Bidi Control (Bidi_C) ✘
Bidi Mirrored (Bidi_M) ✘
Composition Exclusion (CE) ✘
Case Ignorable (CI) ✘
Changes When Casefolded (CWCF) ✘
Changes When Casemapped (CWCM) ✘
Changes When NFKC Casefolded (CWKCF) ✘
Changes When Lowercased (CWL) ✘
Changes When Titlecased (CWT) ✘
Changes When Uppercased (CWU) ✘
Cased (Cased) ✘
Full Composition Exclusion (Comp_Ex) ✘
Default Ignorable Code Point (DI) ✘
Dash (Dash) ✘
Deprecated (Dep) ✘
Diacritic (Dia) ✘
Emoji Modifier Base (EBase) ✘
Emoji Component (EComp) ✘
Emoji Modifier (EMod) ✘
Emoji Presentation (EPres) ✘
Emoji (Emoji) ✘
Extender (Ext) ✘
Extended Pictographic (ExtPict) ✘
FC NFKC Closure (FC_NFKC) Glyph for U+2205 Empty Set
Grapheme Cluster Break (GCB) Any
Grapheme Base (Gr_Base) ✔
Grapheme Extend (Gr_Ext) ✘
Grapheme Link (Gr_Link) ✘
Hex Digit (Hex) ✘
Hyphen (Hyphen) ✘
ID Continue (IDC) ✘
ID Start (IDS) ✘
IDS Binary Operator (IDSB) ✘
IDS Trinary Operator and (IDST) ✘
IDSU (IDSU) 0
ID_Compat_Math_Continue (ID_Compat_Math_Continue) 0
ID_Compat_Math_Start (ID_Compat_Math_Start) 0
Ideographic (Ideo) ✘
InCB (InCB) None
Indic Mantra Category (InMC) —
Indic Positional Category (InPC) NA
Indic Syllabic Category (InSC) Other
Jamo Short Name (JSN) —
Join Control (Join_C) ✘
Logical Order Exception (LOE) ✘
Modifier Combining Mark (MCM) ✘
Math (Math) ✔
Noncharacter Code Point (NChar) ✘
NFC Quick Check (NFC_QC) Yes
NFD Quick Check (NFD_QC) Yes
NFKC Casefold (NFKC_CF) Glyph for U+2205 Empty Set
NFKC Quick Check (NFKC_QC) Yes
NFKC_SCF (NFKC_SCF) Glyph for U+2205 Empty Set
NFKD Quick Check (NFKD_QC) Yes
Other Alphabetic (OAlpha) ✘
Other Default Ignorable Code Point (ODI) ✘
Other Grapheme Extend (OGr_Ext) ✘
Other ID Continue (OIDC) ✘
Other ID Start (OIDS) ✘
Other Lowercase (OLower) ✘
Other Math (OMath) ✘
Other Uppercase (OUpper) ✘
Prepended Concatenation Mark (PCM) ✘
Pattern Syntax (Pat_Syn) ✔
Pattern White Space (Pat_WS) ✘
Quotation Mark (QMark) ✘
Regional Indicator (RI) ✘
Radical (Radical) ✘
Sentence Break (SB) Other
Soft Dotted (SD) ✘
Sentence Terminal (STerm) ✘
Terminal Punctuation (Term) ✘
Unified Ideograph (UIdeo) ✘
Variation Selector (VS) ✘
Word Break (WB) Other
White Space (WSpace) ✘
XID Continue (XIDC) ✘
XID Start (XIDS) ✘
Expands On NFC (XO_NFC) ✘
Expands On NFD (XO_NFD) ✘
Expands On NFKC (XO_NFKC) ✘
Expands On NFKD (XO_NFKD) ✘
Bidi Paired Bracket (bpb) Glyph for U+2205 Empty Set
Bidi Paired Bracket Type (bpt) None
East Asian Width (ea) neutral
Hangul Syllable Type (hst) Not Applicable
ISO 10646 Comment (isc) —
Joining Group (jg) No_Joining_Group
Joining Type (jt) Non Joining
Line Break (lb) Alphabetic
Numeric Type (nt) none
Numeric Value (nv) not a number
Simple Case Folding (scf) Glyph for U+2205 Empty Set
Script Extension (scx)
Vertical Orientation (vo) R