Entities in LUIS

Entities are important words in utterances that describe information relevant to the intent, and sometimes they are essential to it. Entities belong to classes of similar objects.

In the utterance "Book me a ticket to Paris", "Paris" is an entity of type location. By recognizing the entities that are mentioned in the user’s input, LUIS helps you choose the specific actions to take to fulfill an intent.

You do not need to create entities for every concept in your app, but only for those required for the app to take action. You can add up to 30 entities in a single LUIS app.

You can add, edit or delete entities in your app through the Entities list on the Entities page in the LUIS app web portal. LUIS offers many types of entities; prebuilt entities, custom machine learned entities and list entities.

Types of entities

LUIS offers the following types of entities:

Type Description
Prebuilt Built-in types that represent common concepts like dates, times, and geography.
These don't count towards the maximum number of entities you may use in your LUIS app. See Prebuilt entities for more information.
List List entities represent a fixed set of synonyms or related words in your system. Each list entity may have one or more synonyms. They aren't machine learned, and are best used for a known set of variations on ways to represent the same concept. List entities don't have to be labeled in utterances or trained by the system.
A list entity is an explicitly specified list of values. Unlike other entity types, LUIS does not discover additional values for list entities during training. Therefore, each list entity forms a closed set.

Your app may use up to 50 list entities, and they don't count toward the maximum 30 you may use. Each list can contain up to 20000 items.
Simple A simple entity is a generic entity that describes a single concept.

These count towards the maximum number of entities you may use.
Hierarchical A hierarchical entity defines a category and its members. It is made up of child entities that form the members of the category. You can use hierarchical entities to define hierarchical or inheritance relationships between entities, in which children are subtypes of the parent entity.

For example, in a travel agent app, you could add hierarchical entities like these:
  • $Location, including $FromLocation and $ToLocation as child entities that represent origin and destination locations.
  • $TravelClass, including $First, $Business, and $Economy as child entities that represent the travel class.
A hierarchical entity can consist of up to 10 child entities.
These count towards the maximum number of entities you may use.
Composite A composite entity is made up of other entities that form parts of a whole. A composite entity can consist of up to 20 child entities.
These count towards the maximum number of entities you may use.

Next steps

See Add entities to learn more about how to add entities to your LUIS app.