U+2148 "ⅈ" Double-Struck Italic Small I Unicode Character

U+2148 "ⅈ" Double-Struck Italic Small I is a typographic symbol from the Letterlike Symbols block, designed to represent the imaginary unit in mathematical notation, often used in contexts where a clear distinction from the standard letter "i" is needed to avoid confusion with other variables. It features a double-struck, or blackboard bold, style combined with an italic slant, mimicking handwritten mathematical convention. This character is particularly common in fields such as complex analysis and engineering, where it denotes the square root of negative one while ensuring visual consistency with other double-struck symbols like the real numbers ℝ or integers ℤ.

General Properties

Code Point	U+2148
Version Added	3.2
Name	Double-Struck Italic Small I
Block	Letterlike Symbols
General Category	Lowercase Letter
Canonical Combining Class	Not Reordered
Bidirectional Class	Left To Right
Decomposition Type	Font
Decomposition Mapping	"i" U+0069 Latin Small Letter I

Encodings

HTML Decimal Encoding	ⅈ
HTML Hex Encoding	ⅈ
UTF-8 Encoding	0xE2 0x85 0x88
UTF-16 Encoding	0x2148
UTF-32 Encoding	0x00002148
C/C++/Java Escape	\u2148

Unicode Properties

NFC Quick Check	Yes
NFD Quick Check	Yes
Numeric Type	None
Numeric Value	NaN
Line Break	Alphabetic
Lowercase	Yes
Cased	Yes
Changes When NFKC Casefolded	Yes
NFKC Casefold	"i" U+0069 Latin Small Letter I
NFKC Simple Casefold	"i" U+0069 Latin Small Letter I
Script	Common
Script Extensions	Common
Indic Syllabic Category	Other
ID Start	Yes
XID Start	Yes
ID Continue	Yes
XID Continue	Yes
Soft Dotted	Yes
Alphabetic	Yes
Math	Yes
Other Math	Yes
Vertical Orientation	Upright
Grapheme Base	Yes
Grapheme Cluster Break	Other
Word Break	Alphabetic letter
Sentence Break	Lower