What is meant when a universal quadratic form is ternary?

Question

I am reading about quadratic forms from class notes of a senior and I am not able to understand what this terminology means:

A quadratic form is universal over K if it represents all totally positive algebraic integers $\alpha \in {O_K}^{+}$.

But what is meant when a universal form is "ternary"?

Kindly tell.

Answer 1

It means that this quadratic form has 3 variables.