diff --git a/model-basics.Rmd b/model-basics.Rmd
index 8e345c5..2f27798 100644
--- a/model-basics.Rmd
+++ b/model-basics.Rmd
@@ -223,7 +223,7 @@ These are exactly the same values we got with `optim()`! Behind the scenes `lm()
     to the linear model.
 
 1.  One challenge with performing numerical optimisation is that it's only
-    guaranteed to find one local optima. What's the problem with optimising
+    guaranteed to find one local optimum. What's the problem with optimising
     a three parameter model like this?
     
     ```{r}