Webster's Revised Unabridged Dictionary · 1913

Vector

Vector , noun

[Latin, a bearer, carrier. from vehere, vectum, to carry.]

1.
Same as Radius vector.
2.
(Mathematics) A directed quantity, as a straight line, a force, or a velocity. Vectors are said to be equal when their directions are the same and their magnitudes equal. Compare Scalar.

In a triangle, either side is the vector sum of the other two sides taken in proper order; the process finding the vector sum of two or more vectors is vector addition (see under Addition).