diff --git a/intro.Rmd b/intro.Rmd
index abe9a72..d59f072 100644
--- a/intro.Rmd
+++ b/intro.Rmd
@@ -109,7 +109,7 @@ To run the code in this book, you will need to install both R and the RStudio ID
 
 ### RStudio
 
-RStudio is an integrated development environment, or IDE, for R programming. There are three key regions in interface:
+RStudio is an integrated development environment, or IDE, for R programming. There are three key regions in the interface:
 
 ```{r echo = FALSE, out.width = "75%"}
 knitr::include_graphics("diagrams/intro-rstudio.png")