diff --git a/program.Rmd b/program.Rmd
index 660ce86..e881d1b 100644
--- a/program.Rmd
+++ b/program.Rmd
@@ -20,7 +20,7 @@ In the following chapters, you'll learn important programming skills:
     and functional programming.
     
 1.  As you start to write more powerful functions, you'll need a solid
-    grouning in R's data structures. You must master the four common atomic 
+    grounding in R's data structures. You must master the four common atomic 
     vectors, the three important S3 classes built on top of them, and
     understand the mysteries of the list and data frame.