# Build a Multi-Line Chart
## **What is a multi-line chart**
A multi-line chart is a type of cartesian chart that displays information as multiple series of data points connected by straight line segments progressing over a period of time.
There are two types of multi-line chart:
1. **Single entity**: it shows the evolution of multiple values of the same entity over time (for example, by comparing the average price of different products in a given time range).
2. **Multiple entity:** it shows the evolution of more entities over time (for example, by comparing for example revenues and costs of a product).
## **When it’s used**
Similar to the [single line chart ](/crystal-console/topics-configuration/visualizations/single-line.md)because they are both based on time, the multiple line chart adds on top of the time also the comparison between entities or values: it offers a more complex visualization with more insights and it can be, therefore, more complex to read and configure.
It is used to show and compare data changes at equal intervals of time, like for monitoring multiple numerical data (e.g. sales, impressions, users, count number of categories…) over a period of time.
This chart is available only when an **over time objective** is selected: this objective shows the evolution of two or more data sets in a given amount of time. For example if each line of the visualization represents a country, you would have the opportunity to compare sales across different countries over time.
Remember that if you need to show the evolution of a measure within a category (strings, text or words instead of numbers, dates or time), you must use a column chart.
If you want to know more about objectives and visualizations, check out [**Objectives and visualizations: what they are and how they work.**](/crystal-console/topics-configuration/configure/objectives-and-visualizations.md)
## **How to configure a single entity multiple line chart**
In order to build a single entity multiple line chart, you have to select a data table that includes at least one column with times series data type, to show how an item evolves over time.
The **Y-axis** will indicate the data source column from which you are getting the insight (e.g. sales or product). The **X-axis** will indicate the given period of time you want to monitor (e.g. month or year).
The **category** will indicate the breakdown you want to get (for example, if your Y axis is product, you can select “product categories”).
For some categories, if you have numeric values, you will need to set up a data bin. See [here](/crystal-console/topics-configuration/configure/data-binning.md) how to do it.
The result of this configuration will be a visualization where the different categories will be shown with different colored lines, that might not be continuous in case there are gaps (for example data related to days or weeks that are missing).
## **How to configure a multi entity multiple line chart**
This chart will allow you to have different columns from the data source on the Y axis.
You will have the opportunity to have a more granular view of your insight: given that your main entity is product, you can see for example a comparison between revenues and costs for the given product.
The result of this configuration will be a visualization where the different categories will be shown with different colored lines.
The multiple line chart visualization is helpful if you want to make a comparison between two or more values, for example if you need to compare sales across different countries over time.
We hope that this article helped you! Do you want to know how to build a list table? Check [this](/crystal-console/topics-configuration/visualizations/list-table.md) out!
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