Leonard Euler (1707-1783) gave us a number of symbols. They are listed below.
| f(x) | for functional notation |
| e | for the base of natural logarithms |
| a, b, c | for the sides of triangle ABC |
| for the summation sign |
| i | for the imaginary unit, the square root of -1 |
Thomas Harriot (1560-1621), usually considered the founder of the English school of algebraists, was the first to use the signs > and < for "is greater than" and "is less than," respectively.
Gottfried Wilhelm Leibniz (1646-1716) gave us our intersection symbol, 
, and union symbol, 
, from set theory.
In 1808 Christian Kramp (1760-1826) of Strassbourg introduced n! for factorial n (or n factorial). The previous symbol was causing printing difficulties.
John Wallis (1616-1703), a mathematician and one of the first to create a system for teaching deaf mutes, introduced our present symbol for infinity 
.