### noun

**(1) **The cardinal number that is the sum of three and one

### Etymology

From

*quaternioun*, from

*quaterniō*, from

*quaternī* (ablative form of

*quater*, “four times”) +

*-iōn*, “-ion”.

### Noun

- A group or set of four people or things.
- A four-dimensional hypercomplex number that consists of a real dimension and 3 imaginary ones (
*i*, *j*, *k*) that are each a square root of -1. They are commonly used in vector mathematics and three-dimensional games. Quaternion multiplication is the most common technique used by mathematicians to avoid gimbal lock when rotating vectors.