Answer:
Though I am only two words I have thousands of letters in me
People need me yet they give me away every day.
The more you work, the more I'll eat.You keep me full, I'll keep you neat. What am I?
Adored by few, feared and hated by many. Mistress of the entire universal reason, master in the art of numbers. Some may have solved many of my mysteries, but there are still many of them to find. What am I?
My head and tail both equal are my middle slender as a bee. Whether I stand on head or heel Is quite the same to you or me. But if my head should be cut off the matter's true though passing strange directly I to nothing change.
No matter how little or how much you use me, you change me every month.