U+210D DoubleStruck Capital H
U+210D was added in Unicode version 1.1 in 1993. It belongs to the block
This character is a Uppercase Letter and is commonly used, that is, in no specific script.
The glyph is a font version of the glyph
The Wikipedia has the following information about this codepoint:
In mathematics, the quaternion number system extends the complex numbers. Quaternions were first described by the Irish mathematician William Rowan Hamilton in 1843 and applied to mechanics in threedimensional space. The algebra of quaternions is often denoted by H (for Hamilton), or in blackboard bold by $H.$ Although multiplication of quaternions is noncommutative, it gives a definition of the quotient of two vectors in a threedimensional space. Quaternions are generally represented in the form
where the coefficients a, b, c, d are real numbers, and 1, i, j, k are the basis vectors or basis elements.
Quaternions are used in pure mathematics, but also have practical uses in applied mathematics, particularly for calculations involving threedimensional rotations, such as in threedimensional computer graphics, computer vision, magnetic resonance imaging and crystallographic texture analysis. They can be used alongside other methods of rotation, such as Euler angles and rotation matrices, or as an alternative to them, depending on the application.
In modern terms, quaternions form a fourdimensional associative normed division algebra over the real numbers, and therefore a ring, also a division ring and a domain. It is a special case of a Clifford algebra, classified as ${\mathrm{Cl}}_{0,2}\left(R\right)\cong {\mathrm{Cl}}_{3,0}^{+}\left(R\right).$ It was the first noncommutative division algebra to be discovered.
According to the Frobenius theorem, the algebra $H$ is one of only two finitedimensional division rings containing a proper subring isomorphic to the real numbers; the other being the complex numbers. These rings are also Euclidean Hurwitz algebras, of which the quaternions are the largest associative algebra (and hence the largest ring). Further extending the quaternions yields the nonassociative octonions, which is the last normed division algebra over the real numbers. The next extension gives the sedenions, which have zero divisors and so cannot be a normed division algebra.
The unit quaternions give a group structure on the 3sphere S^{3} isomorphic to the groups Spin(3) and SU(2), i.e. the universal cover group of SO(3). The positive and negative basis vectors form the eightelement quaternion group.
Representations
System  Representation 

Nº  8461 
UTF8  E2 84 8D 
UTF16  21 0D 
UTF32  00 00 21 0D 
URLQuoted  %E2%84%8D 
HTML hex reference  ℍ 
Wrong windows1252 Mojibake  â„ 
HTML named entity  ℍ 
HTML named entity  ℍ 
L^{A}T_{E}X  \mathbb{H} 
Related Characters
Confusables
Elsewhere
Complete Record
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1.1 (1993)  
DOUBLESTRUCK CAPITAL H  
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