# How do electron donor groups affect the polarity of an O-H bond in alcohol?

My textbook (Chapter Alcohols) , says:

An electron releasing group ($\ce{-CH3}$, $\ce{-C2H5}$) increases the electron density on oxygen tending to decrease the polarity of $\ce{O-H}$ bond.

Now, my question is that if the electron density increases on oxygen, then shouldn't the polarity of the bond increase? Why does it decrease instead?