The questions "What is an exponential functions?" and "What is a natural exponential functions?" are both examples of poor English grammar.
Perhaps you meant:
"What are exponential functions?" and "What are natural exponential functions?"
An exponential function is a function where the variable is in the exponent. A natural exponential function is an exponential function that has the Euler number, , as the base.
Example of a general exponential function:
Example of a natural exponential function:
John
My calculator said it, I believe it, that settles it
