My teacher, textbook and the internet have differing definitions. First of all: Equivalent. My teacher says that two parallel vectors with the same magnitude are equivalent, but my textbook says that two vectors in the same direction are equivalent. ×--> <--× are these equivalent? And Collinear. I can't find any lesson on collinear vectors online. All the definitions say two points are collinear when they lie on the same line, but nothing about vectors. My textbook says "Vectors are collinear if they can be translated so that their start and end points lie on the same line" But my teacher says two vectors are collinear if one is a scalar multiple of the other So first, to clarify, magnitude has no impact on whether two vectors are collinear? And second, the textbook definition seems to be describing parallel vectors. ×--> ×-----> Are these collinear? They can be translated to be on the same line. <---×---> Are these collinear? They are scalar multiples (negative 1) of each other. <---× ×---> What about these?