# U+2149 DOUBLE-STRUCK ITALIC SMALL J

U+2149 was added to Unicode in version 3.2 (2002). It belongs to the block Letterlike Symbols in the Basic Multilingual Plane.

This character is a Lowercase Letter and is commonly used, that is, in no specific script.

The glyph is a Font composition of the glyphs . It has a Neutral East Asian Width. In bidirectional context it acts as Left To Right and is not mirrored. The glyph can, under circumstances, be confused with 26 other glyphs. In text U+2149 behaves as Alphabetic regarding line breaks. It has type Lower for sentence and ALetter for word breaks. The Grapheme Cluster Break is Any.

The term imaginary unit or unit imaginary number refers to a solution to the equation x2 = −1. As a convention, the solution is usually denoted i. Since there is no real number with this property, it extends the real numbers, and under the assumption that the familiar properties of addition and multiplication (namely closure, associativity, commutativity and distributivity) continue to hold for this extension, the complex number system is generated by including it.

Imaginary numbers are an important mathematical concept, which extends the real number system ℝ to the complex number system ℂ, which in turn provides at least one root for every nonconstant polynomial P(x) (see Algebraic closure and Fundamental theorem of algebra). The term "imaginary" is used because there is no real number having a negative square.

There are two complex square roots of −1, namely i and −i, just as there are two complex square roots of every real number other than zero, which has one double square root.

In contexts where i is ambiguous or problematic, j or the Greek ι is sometimes used (see § Alternative notations). In the disciplines of electrical engineering and control systems engineering, the imaginary unit is often denoted by j instead of i, because i is commonly used to denote electric current.

For the history of the imaginary unit, see Complex number § History.

## Representations

System Representation
8521
UTF-8 E2 85 89
UTF-16 21 49
UTF-32 00 00 21 49
URL-Quoted %E2%85%89
HTML-Escape &#x2149;
Wrong windows-1252 Mojibake â

## Complete Record

Property Value
Age (age) 3.2
Unicode Name (na) DOUBLE-STRUCK ITALIC SMALL J
Unicode 1 Name (na1)
Block (blk) Letterlike_Symbols
General Category (gc) Lowercase Letter
Script (sc) Common
Bidirectional Category (bc) Left To Right
Combining Class (ccc) Not Reordered
Decomposition Type (dt) Font
Decomposition Mapping (dm)
Lowercase (Lower)
Simple Lowercase Mapping (slc)
Lowercase Mapping (lc)
Uppercase (Upper)
Simple Uppercase Mapping (suc)
Uppercase Mapping (uc)
Simple Titlecase Mapping (stc)
Titlecase Mapping (tc)
Case Folding (cf)
ASCII Hex Digit (AHex)
Alphabetic (Alpha)
Bidi Control (Bidi_C)
Bidi Mirrored (Bidi_M)
Bidi Paired Bracket (bpb)
Bidi Paired Bracket Type (bpt) None
Cased (Cased)
Composition Exclusion (CE)
Case Ignorable (CI)
Full Composition Exclusion (Comp_Ex)
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)
Dash (Dash)
Deprecated (Dep)
Default Ignorable Code Point (DI)
Diacritic (Dia)
East Asian Width (ea) Neutral
Extender (Ext)
FC NFKC Closure (FC_NFKC)
Grapheme Cluster Break (GCB) Any
Grapheme Base (Gr_Base)
Grapheme Extend (Gr_Ext)
Hex Digit (Hex)
Hangul Syllable Type (hst) Not Applicable
Hyphen (Hyphen)
ID Continue (IDC)
Ideographic (Ideo)
ID Start (IDS)
IDS Binary Operator (IDSB)
IDS Trinary Operator and (IDST)
InMC (InMC)
Indic Positional Category (InPC) NA
Indic Syllabic Category (InSC) Other
ISO 10646 Comment (isc)
Joining Group (jg) No_Joining_Group
Join Control (Join_C)
Jamo Short Name (JSN)
Joining Type (jt) Non Joining
Line Break (lb) Alphabetic
Logical Order Exception (LOE)
Math (Math)
Noncharacter Code Point (NChar)
NFC Quick Check (NFC_QC) Yes
NFD Quick Check (NFD_QC) Yes
NFKC Casefold (NFKC_CF)
NFKC Quick Check (NFKC_QC) No
NFKD Quick Check (NFKD_QC) No
Numeric Type (nt) None
Numeric Value (nv) NaN
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)
Pattern Syntax (Pat_Syn)
Pattern White Space (Pat_WS)
Quotation Mark (QMark)
Sentence Break (SB) Lower
Simple Case Folding (scf)
Script Extension (scx) Common
Soft Dotted (SD)
STerm (STerm)
Terminal Punctuation (Term)
Unified Ideograph (UIdeo)
Variation Selector (VS)
Word Break (WB) ALetter
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)