# What is the Expression and how to use it

## What is the Expression and How to Use It

Expression evaluation is the **first step** of Delpha’s duplicate detection process. An **Expression** is a formula that determines whether two records are a **100% match** based on specific fields. It can use logical **AND**, **OR**, or a **combination** of both.

> Expressions are configured using JSON-style syntax and must use fields defined in the **Fields** section.

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From version 3.56, we've replaced the old JSON-based interface with a [new visual rule builder to simplify and streamline duplicate rule configuration.](https://help.delpha.io/delpha-upgrade/whats-new/duplicate/build-3.56#visual-rule-builder-for-duplicate-management)
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## Expression Syntax Explained

| **Expression Type**                                                         | **Example**                                                   | **What it Means**                                                                 |
| --------------------------------------------------------------------------- | ------------------------------------------------------------- | --------------------------------------------------------------------------------- |
| <p><strong>AND:</strong> </p><p> <code>\[\["field1", "field2"]]</code></p>  | `[["Email", "Name"]]`                                         | Records match if **both** Email and Name are the same.                            |
| <p><strong>OR:</strong> </p><p><code>\[\["field1"], \["field2"]]</code></p> | `[["Email"], ["Phone"]]`                                      | Records match if **either** Email or Phone is the same.                           |
| Combination of `AND` & `OR`                                                 | `[["LinkedInURL1__c", "LinkedInURL2__c"], ["Name", "Email"]]` | Records match if either **LinkedIn URLs match** or **Name and Email** both match. |

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#### Important Notes

* Fields used in the Expression **must be configured** in the *Fields section* of your duplicate detection settings.
* Expressions **only identify exact matches** and are often used to complement fuzzy matching algorithms later in the process.
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