Given two points, A and B, there are two vectors: A-->B and A<--B which are parallel but pointing in opposite directions. I remember learning as a kid a word which simply defines the line upon which the vectors lie and another which defines the direction the vectors move along the line, something like "A-->B and A<--B have the same XXX, but opposite YYY." Can anyone fill in these blanks?

  • All I can find is "opposite vector" or "negative vector". Is it something other than that?
    – Catija
    Jun 29, 2015 at 19:59
  • I expect you would get an answer quicker on math.stackexchange.com
    – Avon
    Jun 29, 2015 at 20:00
  • @Catija No, I distinctly remember the structure being as given: "A-->B and A<--B have the same XXX, but opposite YYY".
    – Wasabi
    Jun 29, 2015 at 20:01
  • 2
    Opposite sense.
    – Colin Fine
    Jun 29, 2015 at 20:10
  • Your title doesn't clearly reflect the content of the body, and I think my answer reflects the title more than the body. Is my answer appropriate, or should I delete it? Jun 29, 2015 at 20:44

3 Answers 3


same magnitude and opposite direction


The vectors are called antiparallel:

In a Euclidean space, two directed line segments, often called vectors in applied mathematics, are antiparallel, if they are supported by parallel lines and have opposite directions.

Note: Two antiparallel vectors need not have the same magnitude (i.e. length); they can be of any length.


same axis but opposite direction?

  • Axis? For a vector? Never heard that used in this context.
    – Drew
    Jun 29, 2015 at 20:37

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.