diff --git a/units/en/unit2/glossary.mdx b/units/en/unit2/glossary.mdx
index a8365e9..c4b5dce 100644
--- a/units/en/unit2/glossary.mdx
+++ b/units/en/unit2/glossary.mdx
@@ -27,6 +27,10 @@ This is a community-created glossary. Contributions are welcomed!
 - Does not include any exploration.
 - Can be disadvantageous in environments with uncertainty or unknown optimal actions.
 
+### Off-policy vs on-policy algorithms
+
+- **Off-policy algorithms:** A different policy is used at training time and inference time
+- **On-policy algorithms:** The same policy is used during training and inference
 
 If you want to improve the course, you can [open a Pull Request.](https://github.com/huggingface/deep-rl-class/pulls)
 
@@ -34,3 +38,4 @@ This glossary was made possible thanks to:
 
 - [Ramón Rueda](https://github.com/ramon-rd)
 - [Hasarindu Perera](https://github.com/hasarinduperera/)
+- [Arkady Arkhangorodsky](https://github.com/arkadyark/)