Possibly the letters with no lines of symmetry.
A-P
A
A
g.
There are many ways to solve different maths codes. some may work with numbers turning into letters others may work with letters turning into different letters. some codes may have a letter 3 letters after it so say if the code was; ALD. 3 letters after A is D 3 letters after L is O and 3 letters after D is G so the word would spell "dog".
dad add
If you mean d*r = r*d (where * means multiply_ then it is the commutative property.
Only 2: CD and DC.
D
Next three letters are: e n d
K - The pattern is to skip one letter of the alphabet in between each - between D and F there would usually be a "D", between F and H a "G" and so on.
y....all others come just two letters after every vovels..
H & I
dynasty, drafty,
e
g.
grape
type in: "ABCD" in the input line.
only answer I can think of is the following 5 letters: t, o, d, a, y
A movie that has a 6 letter word in the title that uses the letters Y-O-D-B-L-O is "Bloody Mary".