What is the sense of a vector? Is the sense the same thing as the direction of a vector? If yes, why should we use the term sense instead of direction?
Can anyone illustrate it?
 A: Have a look at this article on vector algebra. In this context sense is a technical term. The relevent extracts from the article are:

Vectors are quantities that require the specification of magnitude, orientation,
  and sense. The characteristics of a vector are the magnitude, the orientation, and the
  sense.
The orientation of a vector is specified by the relationship between the vector
  and given reference lines and/or planes.
The sense of a vector is specified by the order of two points on a line parallel to
  the vector.
Orientation and sense together determine the direction of a vector.

So the orientation tells you what angle the vector is and the sense tells you which way it's pointing.
A: The term "direction" was probably not the best choice of words. Consider this example - a car travelling at 30mph down Smith Street, heading west. Smith Street becomes the direction (or the defined path), west becomes the sense. Simply saying "30mph down Smith Street" would not be enough information. It all comes down to a poor choice of words (or change of meaning over time or a poor translation). In that regard, "orientation" is a better choice than "direction".
