# How do you read an expression such as e^{-rt}

I heard people say that the exponential to the power of R times T

e^{rt}

Is it normal?

e^{-rt}

the exponential to the negative power of R times T

or

the exponential to the power of negative R times T

or

the exponential to the negative exponent of R times T

• sometimes I say, "e to the (negative) r t" Jan 14, 2021 at 1:48
• For the other situation, do you say "e to the negative r t"? thx Jan 14, 2021 at 1:50
• How about "the exponential to the negative r t"? Jan 14, 2021 at 1:52
• I think it doesn't matter but I say $e^M$ as "e to the M" whatever M is, so I'd so $e^{-rt}$ as "eee to the negative arrh tee" ... anyway "the exponential to the negative exponent of R times T" doesn't really make any sense. Jan 14, 2021 at 1:53
• No, it is not clear. "The exponential" isn't a thing. "Exponential" is an adjective; you need a noun. There are exponential distributions. There is an exponential function, but the function is not being raised to a power. Jan 14, 2021 at 3:37

The expression e^rt is sloppy. Either write it as $$e^{rt}$$ or e^{rt} so that you won't confuse it with $$e^r\cdot t$$. (The expression $$\exp(rt)$$ is also used very often.)
As long as the context is clear, "$$e$$ to the power of $$rt$$" is a usual way to read it.
Similarly, I would write e^{-rt} or $$e^{-rt}$$ to avoid any confusion. "$$e$$ to the power of negative $$rt$$" is reasonable.