We've defined the signatures, not behaviors. Fixes #2917

src/ch10-02-traits.md

@@ -54,10 +54,10 @@ one per line and each line ends in a semicolon.
 
 ### Implementing a Trait on a Type
 
-Now that we’ve defined the desired behavior using the `Summary` trait, we can
-implement it on the types in our media aggregator. Listing 10-13 shows an
-implementation of the `Summary` trait on the `NewsArticle` struct that uses the
-headline, the author, and the location to create the return value of
+Now that we’ve defined the desired signatures of the `Summary` trait's methods,
+we can implement it on the types in our media aggregator. Listing 10-13 shows
+an implementation of the `Summary` trait on the `NewsArticle` struct that uses
+the headline, the author, and the location to create the return value of
 `summarize`. For the `Tweet` struct, we define `summarize` as the username
 followed by the entire text of the tweet, assuming that tweet content is
 already limited to 280 characters.