Swiss mathematician and physicist Leonhard Euler (1707-1783) is a cornerstone in the field of pure mathematics, offering vital contributions to geometry, calculus, mechanics and number theory.
His association with the St. Petersburg Academy of Sciences fostered his work, developing integral calculus, the theory of trigonometric and logarithmic functions and lending new insights to pure mathematics.
Despite losing his sight, Euler’s work flourished, especially in analytic geometry and trigonometry.

Known for his contribution to the Euler identity and his discovery of the imaginary logarithms of negative numbers, Euler’s textbooks in calculus introduced formulas and methods still used today.
Related: Blaise Pascal Quotes from French Mathematician and Ada Lovelace Quotes from English Mathematician
He introduced common notations such as Σ for the sum, e for the base of natural logarithms and i for √−1.
Euler’s work, spanning number theory to lunar motion, attests to his unparalleled productivity and ingenious use of computational procedures in problem-solving.
Below you will find the best quotes by Leonhard Euler.
Leonhard Euler Quotes

Logic is the foundation of the certainty of all the knowledge we acquire. ~ Leonhard Euler

Now I will have less distraction. ~ Leonhard Euler

For the sake of brevity, we will always represent this number 2.718281828459… by the letter e. ~ Leonhard Euler

Nothing takes place in the world whose meaning is not that of some maximum or minimum. ~ Leonhard Euler.

A function of a variable quantity is an analytic expression composed in any way whatsoever of the variable quantity and numbers or constant quantities. ~ Leonhard Euler.
In the meantime, most noble Sir, you have assigned this question to the geometry of position, but I am ignorant as to what this new discipline involves, and as to which types of problem Leibniz and Wolff expected to see expressed in this way. ~ Leonhard Euler.
To those who ask what the infinitely small quantity in mathematics is, we answer that it is actually zero. Hence there are not so many mysteries hidden in this concept as they are usually believed to be. ~ Leonhard Euler
Although to penetrate into the intimate mysteries of nature and thence to learn the true causes of phenomena is not allowed to us, nevertheless it can happen that a certain fictive hypothesis may suffice for explaining many phenomena. ~ Leonhard Euler

Madam, I have come from a country where people are hanged if they talk. ~ Leonhard Euler
After exponential quantities the circular functions, sine and cosine, should be considered because they arise when imaginary quantities are involved in the exponential. ~ Leonhard Euler
For since the fabric of the universe is most perfect and the work of a most wise Creator, nothing at all takes place in the universe in which some rule of maximum or minimum does not appear. ~ Leonhard Euler
Best Leonhard Euler Quotes
Mathematicians have tried in vain to this day to discover some order in the sequence of prime numbers, and we have reason to believe that it is a mystery into which the human mind will never penetrate. ~ Leonhard Euler.
The kind of knowledge which is supported only by observations and is not yet proved must be carefully distinguished from the truth; it is gained by induction, as we usually say. Yet we have seen cases in which mere induction led to error. Therefore, we should take great care not to accept as true such properties of the numbers which we have discovered by observation and which are supported by induction alone. Indeed, we should use such a discovery as an opportunity to investigate more exactly the properties discovered and to prove or disprove them; in both cases we may learn something useful. ~ Leonhard Euler

Transcendental [numbers], They transcend the power of algebraic methods. ~ Leonhard Euler
Since the fabric of the universe is most perfect and the work of a most wise Creator, nothing at all takes place in the universe in which some rule of maximum or minimum does not appear … there is absolutely no doubt that every affect in the universe can be explained satisfactorily from final causes, by the aid of the method of maxima and minima, as it can be from the effective causes themselves … Of course, when the effective causes are too obscure, but the final causes are readily ascertained, the problem is commonly solved by the indirect method. ~ Leonhard Euler.