- "All pens are fish"
- This means the category of "Pens" is completely contained within the category of "Fish".
- Diagram representation: A small circle labeled Pens completely inside a larger circle labeled Fish.
- "No fish are birds"
- This means the category of "Fish" and the category of "Birds" have absolutely no overlap. They are mutually exclusive.
- Diagram representation: The Birds circle must be drawn completely separate from the Fish circle.
- "No pens are birds"
- Since all pens are safely tucked inside the fish circle, and birds cannot touch the fish circle, it naturally follows that birds cannot touch pens either. The diagram confirms this deduction perfectly.