Gottfried Wilhelm von Leibniz (1646-1716): mathematician, scientist, philosopher.
Coins the term "function": it is necessary to identify the various quantities associated to a curve, including its value, the slope and the perpendicular at one point.
Friedrich Wilhelm Bessel (1784-1846): mathematician, astronomer.
He was the first to determine the distance of a star by measuring the parallax of 61 Cygni in 1838. With his precise observations could categorize the locations of more than 50000 stars and then he introduced mathematical functions now know by his name.