Writing Figure Legends That Actually Stand Alone
A figure legend has one specific job that's easy to underestimate: a reader should be able to understand the figure from the legend alone, without needing to hunt through the main text for context — because that's exactly how most readers actually skim a paper.
What a complete figure legend needs
- A brief title/summary sentence stating what the figure shows
- Definition of any abbreviations used within the figure itself — even if defined elsewhere in the text, repeat it here so the figure is self-contained
- Sample size and key experimental conditions — n numbers, relevant treatment groups, what error bars represent
- Statistical significance markers explained — what * or ** actually means, and what test was used
- Panel labels explained, if the figure has multiple panels (A, B, C)
The "stand-alone" test
A useful check: could someone who has only seen this one figure and its legend — not the rest of your paper — understand what it shows and why it matters? If understanding it requires flipping back to the Methods section to know what "Group 2" means, the legend needs more detail.
⚠️ Error bars and statistics are the most commonly under-explained detail. Always state explicitly what error bars represent (SEM, SD, 95% CI — they are not interchangeable) and what statistical test produced any significance markers shown.
💡 Write legends after finalizing the figure
Write or finalize your figure legends after the figure itself is finished, not before — details often shift during figure revision (a removed data point, a changed axis label), and a legend written earlier can drift out of sync with the final figure.
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