diff --git a/photon.md b/photon.md
index 5935f2596..3ebeca787 100644
--- a/photon.md
+++ b/photon.md
@@ -6,3 +6,4 @@
 - From Wikipedia:
   - > The name photon derives from the Greek word for light, [[φῶς]] (transliterated phôs).
   - > Although Wolfers's and Lewis's theories were contradicted by many experiments and never accepted, the new name was adopted by most physicists very soon after Compton used it.
+  - > In physics, a photon is usually denoted by the symbol [[γ]] (the Greek letter gamma). This symbol for the photon probably derives from gamma rays,