typo fix

draft-ietf-core-coap-pubsub.md

@@ -107,7 +107,7 @@ topic collection:
 : A set of topic configurations. A topic collection is hosted as one collection resource at the broker, and its representation is the list of links to the topic resources corresponding to each topic configuration.
 
 topic-configuration:
-: A set of information concerning a topic, including its configuration and other metadata. A topic configurations is hosted as one topic resource at the broker, and its representation is the set of configuration information concerning the topic. All the topic resources associated with the same topic collection share a common base URI, i.e., the URI of the collection resource. Throughout this document the word "topic" and "topic-configuration" can be used interchangeably.
+: A set of information concerning a topic, including its configuration and other metadata. A topic configuration is hosted as one topic resource at the broker, and its representation is the set of configuration information concerning the topic. All the topic resources associated with the same topic collection share a common base URI, i.e., the URI of the collection resource. Throughout this document the word "topic" and "topic-configuration" can be used interchangeably.
 
 topic-data resource:
 : A resource where clients can publish data and/or subscribe to data for a specific topic. The representation of the topic resource corresponding to such a topic also specifies the URI to the present topic-data resource.