Venn diagram encodes values as intersection area of overlapping closed curves. John Venn, 1880; Euler drew related region diagrams earlier.
In reports, ads and assignments it fits two or three sets with a real overlap story. Skip it when four-plus sets, or when sizes must be to scale.
Rules
- Rules 1 — Use intersection area of overlapping closed curves as one channel, not two.
- Rules 2 — Direct labels beat a distant legend.
- Rules 3 — Do not hide zero. If you break the axis, say so.
- Rules 4 — Colour encodes category or magnitude, not both.
- Rules 5 — Put the claim in the title, not just “Venn diagram”.
- Rules 6 — Source and period, even in small type.
Palette
- Palette 1 — Categories: distinct hues. Sequences: one hue, changing value.
- Palette 2 — Diverging: a neutral centre, emphasis at both ends.
- Palette 3 — One brand colour plus greys beats a rainbow.
- Palette 4 — Check contrast on a projector and in greyscale print.
Type
- Type 1 — Tabular figures for numbers. Do not pour body copy into the chart.
- Type 2 — Titles as sentences; axes as short nouns.
- Type 3 — For CJK, drop weight one step and leave tracking.
Venn diagram: honour intersection area of overlapping closed curves, and switch when four-plus sets, or when sizes must be to scale.