Therefore, if I choose to go to dance class, the opportunity cost is going ice skating with my friends...
but if I choose to go ice skating, the opportunity cost is missing class and having less time to practice my routines.
Opportunity Cost - the next best thing that you are missing out on by choosing something else
Opportunity Cost - An opportunity cost refers to a benefit that a person could have received, but gave up, to take another course of action. Stated differently, an opportunity cost represents an alternative given up when a decision is made. This cost is therefore most relevant for two mutually exclusive events, whereby choosing one event, a person cannot choose the other. Opportunity Cost Definition | Investopedia