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?
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.