Leonhard Euler was a Swiss mathematician and physicist. He developed important concepts and proved mathematical theorems in fields as diverse as calculus, number theory and topology. He introduced much of the modern mathematical terminology and notation, particularly for mathematical analysis, such as the notion of a mathematical function. He is also renowned for his work in mechanics, optics and astronomy. Euler is considered to be the preeminent mathematician of the 18th century and one of the greatest of all time. He is also the most prolific according to the Guinness Book of Records; his collected works fill 60–80 quarto volumes. Euler was featured on the sixth series of the Swiss 10-franc banknote and on numerous Swiss, German and Russian stamps. The asteroid 2002 Euler was named in his honor.