Templates called French Cerves Simmiler to stensills
ANSWER
Here's a site that has an index of well known curves: http://www-groups.dcs.st-and.ac.uk/~history/Curves/Curves.html
You will notice that a "straight line" is on the list. Although straight lines and line segments do not appear to be curved in the usual sense of the term, in the technical language of mathematics, they are treated as "curves."
Associated trivia: Curves constitute the largest (or "strongest" infinity). For example, although the number of whole numbers is infinite, there are more variations of curves than there are whole numbers.