TITLE: Imaginary number
QUESTION [0 upvotes]: In the universe of numbers. Is the square root of negative one the only imaginary number or there exist some more? If more, what are they called? Thank you for the response.

REPLY [1 votes]: There are different types of imaginary numbers. Complex numbers are numbers of the form $z=a+ib$. Imaginary numbers are known as quaternions. 
They satisfy:
$i^2=j^2=k^2=ijk=-1$
Here is a table that might help you understand:
{"set_name": "stack_exchange", "score": 0, "question_id": 1456291}