diff --git a/factors.Rmd b/factors.Rmd
index 411a181..81bbec6 100644
--- a/factors.Rmd
+++ b/factors.Rmd
@@ -92,7 +92,7 @@ ggplot(gss_cat, aes(race)) +
 
 These levels represent valid values that simply did not occur in this dataset. Unfortunately, dplyr doesn't yet have a `drop` option, but it will in the future.
 
-When working with factors, the two most common operations are changing the order of the levels, and changing the values of the levels. Those operation are described in the sections below.
+When working with factors, the two most common operations are changing the order of the levels, and changing the values of the levels. Those operations are described in the sections below.
 
 ### Exercise