diff --git a/lenstronomy/LightModel/light_model_base.py b/lenstronomy/LightModel/light_model_base.py
index 0582557b2..4cb17de07 100644
--- a/lenstronomy/LightModel/light_model_base.py
+++ b/lenstronomy/LightModel/light_model_base.py
@@ -223,10 +223,15 @@ def surface_brightness(self, x, y, kwargs_list, k=None):
         return flux
 
     def light_3d(self, r, kwargs_list, k=None):
-        """Computes 3d density at radius r :param r: 3d radius units of arcsec relative
-        to the center of the light profile :param kwargs_list: keyword argument list of
-        light profile :param k: integer or list of integers for selecting subsets of
-        light profiles."""
+        """Computes 3d density at radius r (3D radius)
+        such that integrated in projection in units of angle results in the projected surface brightness
+
+        :param r: 3d radius units of arcsec relative to the center of the light profile
+        :param kwargs_list: keyword argument list of light profile
+        :param k: integer or list of integers for selecting subsets of light profiles.
+
+        :return: flux density
+        """
         kwargs_list_standard = self._transform_kwargs(kwargs_list)
         r = np.array(r, dtype=float)
         flux = np.zeros_like(r)