diff --git a/PythonicGcodeMachine/Gcode/Rs274/Lexer.py b/PythonicGcodeMachine/Gcode/Rs274/Lexer.py
index ab888cd5aa6378ebfe74fecdc17bec4c626547ab..a161d876d361b7c385d54562afcd757188c3d467 100644
--- a/PythonicGcodeMachine/Gcode/Rs274/Lexer.py
+++ b/PythonicGcodeMachine/Gcode/Rs274/Lexer.py
@@ -78,10 +78,12 @@ class GcodeLexer:
         'TANGENT',
         'TIMES',
 
+        # 'LETTER',
         'A', 'B', 'C', 'D',
-        'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N',
+        'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
         'P', 'Q', 'R', 'S', 'T',
         'X', 'Y', 'Z',
+        'N',
 
         'POSITIVE_INTEGER',
         'POSITIVE_REAL',
@@ -121,6 +123,9 @@ class GcodeLexer:
     t_TANGENT = r'tan'
     t_TIMES = r'\*'
 
+    # clash with acos ... ???
+    # t_LETTER = r'(' + '|'.join('abcd' + 'fghijklm' + 'pqrst' + 'xyz') + ')'
+
     t_A = r'a'
     T_B = r'b'
     t_C = r'c'
@@ -134,7 +139,6 @@ class GcodeLexer:
     t_K = r'k'
     t_L = r'l'
     t_M = r'm'
-    t_N = r'n'
 
     t_P = r'p'
     t_Q = r'q'
@@ -146,6 +150,8 @@ class GcodeLexer:
     t_Y = r'y'
     t_Z = r'z'
 
+    t_N = r'n'
+
     # def t_POSITIVE_INTEGER(self, t):
     #     r'\d+'
     #     t.value = int(t.value)
diff --git a/PythonicGcodeMachine/Gcode/Rs274/Parser.py b/PythonicGcodeMachine/Gcode/Rs274/Parser.py
index 2b4378e18bc41b3d9d93eedaf937fefda30a90b7..7d47cad21485daabdcd86595ce96f097620bdce9 100644
--- a/PythonicGcodeMachine/Gcode/Rs274/Parser.py
+++ b/PythonicGcodeMachine/Gcode/Rs274/Parser.py
@@ -174,6 +174,7 @@ class GcodeParser:
         p[0] = Ast.Word(p[1], p[2])
 
     def p_mid_line_letter(self, p):
+        # LETTER
         '''mid_line_letter : A
                            | B
                            | C