Here's why:

* OH- ions are hydroxide ions. They are responsible for the basic properties of a substance.

* Bases are substances that can accept protons (H+ ions). They do this by releasing hydroxide ions (OH-) into solution.

Key points:

* The more OH- ions a substance has, the stronger the base.

* Bases have a pH greater than 7.

* Common examples of bases include:

* Sodium hydroxide (NaOH)

* Potassium hydroxide (KOH)

* Calcium hydroxide (Ca(OH)2)

* Ammonia (NH3)