Daily riddle #2, %50 prize

Words
48
Reading
1 min
Listen
Play
9y

As always, the first person to answer correctly gets %50 of whatever this post makes!

Forwards my name remains the same,
Unchanged I am in a mirror frame,
I am not odd, nor I am even,
a simple phrase that linguists believe in.

What am I?

Good luck!
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Daily riddle #2, %50 prize | Ecency