What does 1.8e-5 mean or stand for?

e-5 is alternate notation for 10^-5

The e stands for the word exponent, sort of.
so what you have is
1.8 * 10^-5
which is 0.000018

The "e" is the power of 10 (exponent)

1.8E-5 = 1.8 * 10^-5 = 0.000018

It's a hold-over from the old FORTRAN floating-point days. E for single-precision (7 decimal places), D for double-precision (16 decimal places)

Thank you, God bless you two!!!

The notation 1.8e-5 is a way to express a number in scientific notation. Specifically, it represents the number 1.8 multiplied by 10 raised to the power of -5. In other words, it means 1.8 times 10 to the power of -5, which can be written as:

1.8e-5 = 1.8 × 10^(-5) = 0.000018

To understand this notation, it's helpful to know that scientific notation is commonly used to represent very large or very small numbers in a more concise form. In this case, it is used to represent a very small number, which is equivalent to 0.000018.