diff --git a/book/en/src/by-example/app.md b/book/en/src/by-example/app.md
index cef8288523..8840bdbdee 100644
--- a/book/en/src/by-example/app.md
+++ b/book/en/src/by-example/app.md
@@ -12,7 +12,7 @@ The `app` attribute will expand into a suitable entry point and thus replaces th
 
 ## Structure and zero-cost concurrency
 
-An RTIC `app` is an executable system model for since-core applications, declaring a set of `local` and `shared` resources operated on by a set of `init`, `idle`, *hardware* and *software* tasks. In short the `init` task runs before any other task returning the set of `local` and `shared` resources. Tasks run preemptively based on their associated static priority, `idle` has the lowest priority (and can be used for background work, and/or to put the system to sleep until woken by some event). Hardware tasks are bound to underlying hardware interrupts, while software tasks are scheduled by asynchronous executors (one for each software task priority). 
+An RTIC `app` is an executable system model for single-core applications, declaring a set of `local` and `shared` resources operated on by a set of `init`, `idle`, *hardware* and *software* tasks. In short the `init` task runs before any other task returning the set of `local` and `shared` resources. Tasks run preemptively based on their associated static priority, `idle` has the lowest priority (and can be used for background work, and/or to put the system to sleep until woken by some event). Hardware tasks are bound to underlying hardware interrupts, while software tasks are scheduled by asynchronous executors (one for each software task priority). 
 
 At compile time the task/resource model is analyzed under the Stack Resource Policy (SRP) and executable code generated with the following outstanding properties: