Update nomenclature.rst

Author: RDaxini

docs/sphinx/source/user_guide/nomenclature.rst

@@ -163,8 +163,8 @@ There is a convention on consistent variable names throughout the library:
         Temperature of the module
 
     transposition_factor
-        The gain ratio of the radiation on inclined plane to global horizontal
-        irradiation: :math:`\frac{poa\_global}{ghi}`
+        The ratio of the irradiance incident on an inclined plane compared with
+        a horizontal plane, :math:`\frac{poa\_global}{ghi}`
 
     tz
         Timezone