Thirdary
When you forget that tertiary is a word.
Primary, Secondary, Thirdary.
Thirdary
adjective; the last of three items presented in a list; when presenting or discussing three topics or items, the third is presented at the thirdary; next after the second in order; the third level of importantce.
"First, we will save you money; secondary, we will generate new sales; and, thirdary we are fast to implement."