Why direction of angular velocity is taken along the rotational axis?

Question

I read that it is a convention. But what does that mean in physics? If it would have been a sign assigning matter, I could confess but what convention means here? When we decide the direction of linear velocity, it is in real life self-indicating, observable and so it is logical. How can we assign direction to a vector quantity with just saying that it is a convention?

Answer 1

It's not "just a convention" - the direction of angular velocity has direct physical meaning: The direction of angular velocity is the axis around which the object rotates, in the direction given by the right hand rule - if you point your right thumb along the angular velocity, and make the rest of your fingers into a fist, then the direction of the rest of your finger indicates the actual direction of the rotational motion.