Explain what fractional means in the Shading language reference (#4328)

tutorials/shaders/shader_reference/shading_language.rst

@@ -742,7 +742,7 @@ When vec_type (float), vec_int_type, vec_uint_type, vec_bool_type nomenclature i
 +------------------------------------------------------------------------+---------------------------------------------------------------+
 | vec_type **ceil** (vec_type x)                                         | Round to the integer above                                    |
 +------------------------------------------------------------------------+---------------------------------------------------------------+
-| vec_type **fract** (vec_type x)                                        | Fractional                                                    |
+| vec_type **fract** (vec_type x)                                        | Fractional (returns ``x - floor(x)``)                         |
 +------------------------------------------------------------------------+---------------------------------------------------------------+
 | vec_type **mod** (vec_type x, vec_type y)                              | Modulo (division remainder)                                   |
 +------------------------------------------------------------------------+---------------------------------------------------------------+