A plot of the Napierian logarithm for inputs between 0 and 108.The 19 degree pages from Napier's 1614 table of logarithms of trigonometric functions Mirifici Logarithmorum Canonis Descriptio
The term Napierian logarithm or Naperian logarithm, named after John Napier, is often used to mean the natural logarithm. Napier did not introduce this natural logarithmic function, although it is named after him.[1][2]
However, if it is taken to mean the "logarithms" as originally produced by Napier, it is a function given by (in terms of the modern natural logarithm):
The Napierian logarithm satisfies identities quite similar to the modern logarithm, such as[3]
^Larson, Ron; Hostetler, Robert P.; Edwards, Bruce H. (2008). Essential Calculus Early Transcendental Functions. U.S.A: Richard Stratton. p. 119. ISBN978-0-618-87918-2.