Where defined, the first derivative of a monotone function never changes sign, although it may be zero.

Well, since Ron ain't goin, why don't you come on and go along with us two, Susie? / Okeh, Susie grinned. Why not?

Trevor was the firm's facilities manager and it was his job to make sure that their office ran like a well-oiled machine and that the partners, attorneys, and staff were comfortable.

The step-by-step directions walked me through the assembly, but identifying the parts was still hard.