diff --git a/intro.Rmd b/intro.Rmd
index 0bdcb9e..33ef3c5 100644
--- a/intro.Rmd
+++ b/intro.Rmd
@@ -115,6 +115,18 @@ To run the code in this book, you will need to install both R and the RStudio ID
 1. Download and install RStudio, <http://www.rstudio.com/download>.
 1. Install needed packages (see below).
 
+### Code conventions
+
+* In text, we refer to functions in a code font followed by parentheses,
+  for example, `sum()`, or `mean()`.
+
+* We refer to other R objects (like data or function arguments) without
+  parentheses: `flights`, `x`, ...
+  
+* If we want to make it clear which package an object comes from, we'll use
+  the package name followed by two colons: `dplyr::mutate()`, or   
+  `nycflights13::flights`. This is the same convention that R uses.
+
 ### RStudio
 
 RStudio is an integrated development environment, or IDE, for R programming. There are three key regions: