Bluff
A bet with a hand that would lose at showdown: the point is not the cards but the fold. It works if the opponent folds often enough, and «often enough» is an exact number.
A bluff is a bet that wins only if the opponent folds. At showdown the hand loses, and you know it. The price is simple: a half-pot bet pays if the opponent folds more than one time in three; a full-pot bet, more than one time in two. Anything above that bar is profit, anything below is loss, whatever happened in the particular hand.
A pure bluff is a bet with air, no pair and no draw. They are few and expensive. Far more often the bet is a semi-bluff: the hand is worth nothing yet but can get there, and the bet wins two ways, by a fold now or by a card later. How many folds such a move needs depends on how many cards complete it.
An example from session 10
In half an hour, seven pure bluffs, $105 bet, not one took the pot. In the base of earlier sessions a bluff gets through 32% of the time, and zero out of seven comes up about once in fifteen sessions. Each one on its own could have been the right move; together they made the worst session of the series. A bluff is never a mistake because of the result; it is a mistake because of the price.
The same in business
A bluff in business is a promise you could not keep if asked to keep it: a deadline, a price, a volume. It pays in exactly the same way, if it is not checked often enough. And it breaks the same way: not when it is checked once, but when you never knew at what rate of checking it stops paying.
The whole hand is in session 10: “Caution takes fewer steps, and each one costs more”.
The other terms are in the glossary.