XArrow

An extensible relation arrow with labels above and optionally below it.

Property	Default	Meaning
label	"xrightarrow"	One of the extensible MathStretch arrow names.
children	Empty	Upper label.
below	Absent	Lower label.
thickness	em(0.04)	Arrow rule thickness.
head-curve	0.7	Barb curvature from 0 to 1, using ArrowHead geometry.

Labels can be TeX strings or elements and use upper/lower script styles. The larger padded label determines width, subject to the shape's minimum. Each label has half an em of its own size on either side. The arrow sits on the math axis; a deep upper label receives extra clearance. Color and opacity inherit normally.

Arrows use core Arrow and ArrowHead elements with open, joined barbs. Harpoons use single-barbed heads; double shafts and hooks combine them with core lines and arcs. Math controls sizing, the axis, and label placement, while core handles the arrow geometry and rendering.

The TeX form is \xrightarrow[below]{above}. Over/under decorations on a body belong in Accent. See math decorations.