turn
The full turn as a unit — half a turn is written 0.5turn and needs no footnote.
One turn is a complete revolution: 360 degrees, 400 gradians, 2π radians — the same rotation, said in one word. It is the newest and most readable of the four angle units: 0.25turn asks you to remember no number at all.
It is the right choice when the intent is counted in turns: an icon that flips half a turn on opening, a loading animation that spins 3turn, a conic-gradient divided into fractions of the circle. The angle becomes pizza arithmetic — checkable in anyone's head.
.virado {
rotate: 0.25turn;
}