Hello!

Recently, I found in my textbook that says collinearity is not equivalence relation on the set of all vectors. But I don't agree with this statement. Any two vectors are collinear if and only if they are parallel.

So a || a is true.

a||b => b||a is true.

and finally:

a||b ^ b||c =>a || c

which is again true.

What is the problem?