i: irreducible form
n: normal form
-p: parallel transformation
+p: reflexive parallel transformation
+q: sequential transformation
r: reducible form
-s: sequential transformation
+s: strongly normalizing form
- third letter
- forth letter (if present)
+c: proper single step (successor)
e: reflexive transitive closure to normal form (evaluation)
+g: proper multiple step (greater)
p: non-reflexive transitive closure (plus)
q: reflexive closure (question)
s: reflexive transitive closure (star)