---
title: Synonyms in C# SDK
slug: cms-13/docs/synonyms
docTags: 
createdAt: 2026-07-30T20:22:11.023Z
---

Synonym expansion lets a query match related terms beyond the exact value specified in a filter. When you configure synonyms, a filter for a term such as `car` also matches related terms such as `automobile` or `vehicle`. Synonym expansion improves search coverage and returns relevant results when different terms refer to the same concept.

## Prerequisites

Synonym expansion requires a synonym dictionary configured on your Optimizely Graph instance. See [Synonyms](docId\:sNcLLcLYgWv_QVb0Mtqus) for configuration details.

Create or update a synonym dictionary using the `PUT /resources/synonyms` endpoint. If no synonym dictionaries exist, synonym slots have no effect and queries run without expansion.

## How synonym slots work

Optimizely Graph supports two independent synonym slots:

- `SynonymSlot.One`
- `SynonymSlot.Two`

Each slot maps to its own synonym dictionary. Apply a slot to a filter to enable synonym expansion for that query condition.

To use synonym expansion, create filters with the `BuildFilter<T>()` API instead of inline `.Where()` expressions.

```csharp
var filter = client.BuildFilter<ArticlePage>()
    .And(x => x.Author.Contains("search_term", SynonymSlot.One));

var result = await client
    .QueryContent<ArticlePage>()
    .Where(filter)
    .GetAsContentAsync();
```

## Use `Contains` with synonym expansion

Apply synonym expansion to a `Contains` filter:

```csharp
var filter = client.BuildFilter<ArticlePage>()
    .And(x => x.Author.Contains("search_term", SynonymSlot.One));
```

The query matches the provided value and any configured synonyms.

## Use `Match` with synonym expansion

Apply synonym expansion to a `Match` filter for full-text matching:

```csharp
var filter = client.BuildFilter<ArticlePage>()
    .And(x => x.Author.Match("search_term", SynonymSlot.One));
```

The `Match` filter expands the search term through the configured synonym dictionary.

## Use multiple synonym slots

Apply more than one synonym slot to a filter. This expands the query using multiple synonym dictionaries.

```csharp
var filter = client.BuildFilter<ArticlePage>()
    .And(x => x.Author.Contains("search_term", SynonymSlot.One, SynonymSlot.Two));
```

Optimizely Graph evaluates synonyms from both dictionaries when matching results.

## Use `In` with synonym expansion

Apply synonym expansion to an `In` filter to match any value in a list or its synonyms:

```csharp
string[] terms = ["term_one", "term_two"];

var filter = client.BuildFilter<ArticlePage>()
    .And(x => x.Author.In(terms, SynonymSlot.One));
```

The `In` filter returns items where the field matches the specified values or their configured synonyms.

## Combine synonyms with other conditions

Combine synonym filters with additional query conditions:

```csharp
var filter = client.BuildFilter<ArticlePage>()
    .And(x => x.Author.Contains("search_term", SynonymSlot.One))
    .And(x => x.IsFeatured.Match(true));

var result = await client
    .QueryContent<ArticlePage>()
    .Where(filter)
    .GetAsContentAsync();
```

This query returns featured articles where the `Author` field matches the provided value or any configured synonym.