quaternion

A set of four persons or items.

Any number of the form a + bi + cj + dk where a, b, c, and d are real numbers, ij = k, i² = j² = −1, and ij = −ji. Under addition and multiplication, quaternions have all the properties of a field, except multiplication is not commutative.

To divide into quaternions, files, or companies.

A set, group, or body of four: applied to persons or things.

A word of four syllables; a quadrisyllable.

A fourfold quantity capable of being expressed in the form xi + yj + zk + w, where x, y, z, w are scalars, or real numbers, while i, j, k are vectors, or quantities whose squares are negative scalars. The calculus of such quantities is termed quaternions.

In book-making, a set or ‘gathering’ of four sheets of paper or parchment folded in two.

To divide into quaternions, files, or companies.

The number four.

A set of four parts, things, or person; four things taken collectively; a group of four words, phrases, circumstances, facts, or the like.