Is a strong nucleophile a strong base?

Why the oxygen of a hydroxyl group act as a nucleophile or a base?

• Answer:

  The hydroxyl group is the common denomination for a molecule consisting of an oxygen and a hydrogen atom connected by a covalent bond, in other words a O-H, where the oxygen atom has two or three (in case its an hydroxide anion) pair of free electrons, which can attack another atom with a deficiency of electrons and make a bond (acting like a nucleophile) or the same thing but attacking a proton H+ (atom with deficiency of electrons) acting in this case as a base. In both cases it acts as a nucleophile but when it attacks a proton or a molecule with a proton (like an acid) acts specifically as a base. I hope I could answer your question.