cap
The height of the capitals — the top of the H, measured by the font itself.
One cap is the cap height of the font: from the baseline to the top of the H. It is ex's upstairs sister — one measures the core of the lowercase, the other the ceiling of the capitals — and when the metric is missing from the font, the browser falls back to an approximation taken from the glyphs themselves.
Its classic calling is icons aligned to text: an SVG with height: 1cap touches the ceiling of the neighboring capitals at any size, without the pixel nudges every icon alignment seems condemned to.
HH
.icone-inline {
height: 1cap;
width: auto;
}