The standard unit of measurement used to describe the amount an individual cares about something.
Fucks are an unofficial part of the metric system and follow the same rules. ie: one-thousand fucks are equal to one kilofuck.
The fuck is almost always used to describe how little someone cares about something and the amount of fucks someone gives can be detected by a fuck-o-meter.
Guy 1: You ready for the spanish exam today?
Guy 2: nope.
Guy 1: I was up studying all night and I'm still screwed.
Guy 2: I give... zero fucks.
*Fuck-o-meter confirms 0 fucks given*