# Cohort

> A chart word, with the charts that use it.

**Definition.** A cohort is a group that started in the same period, followed over time. Comparing cohorts shows whether newer groups hold on better than older ones.

Updated Nov 2, 2026

## 026 · Cohort

- **01 One cohort.** Each row is the group that started in one month.
- **02 Months since start.** Each column is one month after the start, M0 to M5.

## Where you see it

- [026 · Cohort](https://usechartory.com/charts/cohort): Change over time · SaaS data

## Common mistakes

- **Mixing calendar months and months since start** A cohort chart lines rows up by age, not by date. Keep the columns as months since start.
- **Small cohorts read like big ones** Show each cohort's size next to its label.

## Questions

### Why is a cohort chart a triangle?

Newer cohorts have fewer months behind them, so each row is shorter.

### What is a cohort in SaaS?

Usually the customers who signed up or started paying in the same month.

## Related terms

- [Time series](https://usechartory.com/glossary/time-series): Values recorded at regular moments, drawn left to right.
- [Share](https://usechartory.com/glossary/share): A part divided by its total, read as a percent.
- [Series](https://usechartory.com/glossary/series): One set of values drawn together, such as one line or one colour of bars.

## Cohort and the other types.

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