- a logarithm having e as a base. Symbol: ln
- a logarithm to the base e. Usually written log e or lnAlso called: Napierian logarithm Compare e (def. 1), common logarithm
- A logarithm using base e. Natural logarithms are common in mathematics, especially in cases involving complex numbers. They are also called Napierian logarithms, after their inventor, English mathematician John Napier (1550-1617). See more at e. Compare common logarithm.