Common sense is practical wisdom about everyday life that most people in a community share. It's knowing that you should look both ways before crossing the street, that ice is slippery, or that if you don't study for a test, you'll probably do poorly. Common sense tells you what's reasonable and sensible in ordinary situations.

The phrase combines two simple words: common (shared by many people) and sense (good judgment). When we say something is “just common sense,” we mean it's so obviously true or reasonable that it shouldn't need explaining. If your friend suggests swimming during a lightning storm, you'd use common sense to recognize that's dangerous and refuse.

Common sense develops through experience and observation. A five-year-old might not have the common sense to know that a hot stove will burn them, but a ten-year-old has learned this lesson. Some people seem to have more common sense than others: they notice patterns, learn from mistakes, and think ahead about consequences.

Interestingly, what counts as common sense can vary between cultures and time periods. In medieval Europe, people thought bathing was unhealthy (definitely not common sense today!). And common sense in a small farming village might differ from common sense in a big city. Still, certain truths remain universal: treat others with respect, don't touch fire, and look where you're going.

Sometimes highly educated people can lack common sense, knowing complicated theories but struggling with practical, everyday decisions. True intelligence combines book learning with the practical wisdom of common sense.