diff --git a/model-basics.Rmd b/model-basics.Rmd
index 8e56623..5791adc 100644
--- a/model-basics.Rmd
+++ b/model-basics.Rmd
@@ -346,7 +346,7 @@ model_matrix(df, y ~ x1 + x2)
 
 This formula notation is sometimes called "Wilkinson-Rogers notation", and was initially described in _Symbolic Description of Factorial Models for Analysis of Variance_, by G. N. Wilkinson and C. E. Rogers <https://www.jstor.org/stable/2346786>. It's worth digging up and reading the original paper if you'd like to understand the full details of the modelling algebra.
 
-The following sections expand on how this formula notation works for categorcal variables, interactions, and transformation.
+The following sections expand on how this formula notation works for categorical variables, interactions, and transformation.
 
 ### Categorical variables