U+210D "ℍ" Double-Struck Capital H Unicode Character

U+210D "ℍ" Double-Struck Capital H is a typographic symbol belonging to the set of double-struck (blackboard bold) letters, commonly used in mathematics to denote the set of quaternions, which are a number system extending complex numbers. This character is part of the Letterlike Symbols block in Unicode, designed to visually mimic handwriting conventions where special number sets are written with bold or double-struck letters for clarity. Its inclusion in Unicode ensures consistent representation across digital platforms, allowing mathematicians and scientists to precisely denote quaternions in academic papers, online forums, and digital documents without relying on font tricks or formatting workarounds.