The LaTeX command for quaternions (ℍ) is \mathbb{H}.
\mathbb{H}Writing a paper? The table generator and the BibTeX cleaner are one click away, no account.
Write \mathbb{H} inside math mode, that is between $…$ for inline math or in a \[ … \] or equation block for display math. This symbol needs the amssymb package, so add \usepackage{amssymb} to your preamble.
The blackboard-bold letters come from the AMS fonts, so \mathbb{H} needs \usepackage{amssymb}. With unicode-math under XeLaTeX or LuaLaTeX, typing ℍ in a formula gives the same symbol. Not to be confused with \mathbb{C} (ℂ).
$x \in \mathbb{H}$Open this example in the live preview: it renders as you type, with no compiler and no signup.
\mathbb{C} (ℂ): complex numbers\mathbb{O} (𝕆)Number sets in LaTeX: the full table or search all 350+ LaTeX symbols.
Use \mathbb{H} in math mode after adding \usepackage{amssymb} to your preamble. For example, $x \in \mathbb{H}$.
It comes from the amssymb package: add \usepackage{amssymb} to your preamble.