A Venn diagram is a picture that uses overlapping circles to show how different groups of things relate to each other. Imagine you draw one circle for “things that are red” and another circle for “things that are round.” Where the circles overlap, you'd place things that are both red and round, like an apple or a cherry. Things that are only red (like a stop sign) go in the red circle but outside the overlap. Things that are only round (like a basketball) go in the round circle but outside the overlap.

These diagrams are named after John Venn, an English mathematician who popularized them in the 1880s. Teachers often use Venn diagrams to help students compare two stories, two historical figures, or two scientific concepts. You might use one to compare dogs and cats: both are pets (that goes in the overlapping section), but dogs bark and cats meow (those traits go in the separate circles).

The overlapping area is the key: it shows what the groups have in common. The more circles you add, the more complex the relationships become. A Venn diagram turns complicated comparisons into something you can see at a glance, making it easier to spot similarities and differences that might otherwise stay hidden in paragraphs of text.