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From The Collaborative International Dictionary of English v.0.48:

```Quadrantal \Quad*ran"tal\, a. [L. quadrantalis containing the
fourth fourth part of a measure.] (Geom.)
Of or pertaining to a quadrant; also, included in the fourth
part of a circle; as, quadrantal space.
[1913 Webster]

Quadrantal triangle, a spherical triangle having one side
equal to a quadrant or arc of 90[deg].

Quadrantal versor, a versor that expresses rotation through
one right angle.
[1913 Webster]
.
```

From The Collaborative International Dictionary of English v.0.48:

```Versor \Ver"sor\, n. [NL., fr. L. vertere, versus, to turn. See
Version.] (Geom.)
The turning factor of a quaternion.
[1913 Webster]

Note: The change of one vector into another is considered in
quaternions as made up of two operations; 1st, the
rotation of the first vector so that it shall be
parallel to the second; 2d, the change of length so
that the first vector shall be equal to the second.
That which expresses in amount and kind the first
operation is a versor, and is denoted geometrically by
a line at right angles to the plane in which the
rotation takes place, the length of this line being
proportioned to the amount of rotation. That which
expresses the second operation is a tensor. The product
of the versor and tensor expresses the total operation,
and is called a quaternion. See Quaternion.
[1913 Webster]