Functions. Relationship is 1 is to one or many is to one.
So in practical applications. You and your shadow. You and your location. Money as a function of time you cant have the same amount of money at same time like for example it's your break time and your dad gave you 100 pesos and then you bought chicken bbq for 30 pesos now you only have 70 pesos. Another is the philippine nation to our phil president.