necessity and possibility

In general knowledge, "necessity" refers to something that must be true or must happen; it’s unavoidable and essential. For example, if you need food to survive, that's a necessity. On the other hand, "possibility" indicates that something could happen or be true, but it isn’t guaranteed. For instance, it’s possible to win the lottery, but it's not necessary; many people play without winning. In summary, necessity is about what must happen, while possibility is about what might happen within a range of outcomes.