is the notation used in physics and
engineering to denote the logarithm to base * e*, also called the natural
logarithm, i.e.,

The United States Department of Commerce recommends that the notation be used in this way to refer to the natural logarithm (Taylor 1995, p. 33).

Unfortunately, mathematicians in the United States commonly use the symbol to refer to the natural
logarithm, as does `TraditionalForm` typesetting in the Wolfram
Language. The use of
for different purposes by different mathematical communities causes considerable
confusion, so extreme care is needed in determining if the symbol found in the wild refers to or .

The natural logarithm is implemented in the Wolfram Language as `Log`[*x*],
which is equivalent to `Log`[`E`,
*x*].