Definition
Venn diagram
A diagram whose closed regions show set membership; an overlap means an item belongs to both sets.
What it means
Think in yes-or-no steps for each circle. Is the tile a triangle? Is it striped? A striped triangle goes in the overlap because both answers are yes. A plain circle stays outside both. Where an item sits tells membership, not distance or size.
Remember it
Inside each rule it fits; overlap means both.
Example
Sort four tiles by “triangle” and “striped”. A plain triangle goes in triangle only; a striped circle goes in striped only; a striped triangle goes in the overlap; and a plain circle goes outside both regions.
Watch for
Two overlapping circles are not automatically a Venn diagram unless the regions stand for sets and items are placed by membership.
Common mix-up
The overlap means both, not either.
Exact meaning
In a Venn diagram, each named closed region represents a set. An element is placed inside every region for sets it belongs to; overlaps represent intersections, and the area outside the shown regions but inside the universal boundary represents elements in none of those sets.