+ of output from :any:`notmuch-search(1)`
+
+thread:{<notmuch query>}
+ Threads may be searched for indirectly by providing an arbitrary
+ notmuch query in **{}**. For example, the following returns
+ threads containing a message from mallory and one (not necessarily
+ the same message) with Subject containing the word "crypto".
+
+ ::
+
+ % notmuch search 'thread:"{from:mallory}" and thread:"{subject:crypto}"'
+
+ The performance of such queries can vary wildly. To understand
+ this, the user should think of the query **thread:{<something>}**
+ as expanding to all of the thread IDs which match **<something>**;
+ notmuch then performs a second search using the expanded query.