Siri always makes an effort to understand what a user is trying to do with an app and is usually quite good at this. However, sometimes it's tough for Siri to figure out what's going on or what a user is trying to do. To help Siri figure out what a user might mean, you can provide vocabularies. A vocabulary is a set of strings that map to intents, or to parameters for the intent.

There are two ways for you to teach Siri the vocabulary for your app. One way is through a .plist file. This approach is mostly used for when your app has a global vocabulary that applies to all users. If your app can't supply all custom vocabularies in a static file, you can provide them dynamically. This is particularly useful if, for instance, you want to teach Siri about contacts in a messaging app.