Is Sodium Hydroxide an acid?

Hint: An acid is a hydrogen containing substance that has the ability to donate a proton to another substance. A base is a substance that is capable of accepting a proton. Sodium hydroxide reacts vigorously with acid to form salt and water.
Acidic substances are usually identified by their sour taste while bases are identified by their bitter taste.

Complete answer:
Acids are species that dissociate in water to produce ${H^ + }$ ions while bases dissociate in water to produce $O{H^ - }$ ions.
For example, $HCl$ dissociates in water to produce ${H^ + }$ and $C{l^ - }$ions.
Sulfuric acid, nitric acid and chloric acid are some examples of strong acids. Strong acids are those acids that completely dissociate into their constituent ions.
Similarly, Sodium hydroxide is a base because when it is dissolved in water it dissociates into \[N{a^ + }\] and $O{H^ - }$ ions respectively.
This tells us that sodium hydroxide is basic in nature. Hence, sodium hydroxide is a base.

Additional Information: Sodium hydroxide is also known as lye, caustic soda. At room temperature it is found in the form of white solid. It is highly hygroscopic. Today sodium hydroxide is generated mostly by electrolysis of sodium chloride solution. Sodium hydroxide has various applications. It is used in the manufacture of soap, drugs.

Note:
Sodium hydroxide is a strong base because it fully dissociates in water to form hydroxide ions. A weak base does not dissociate completely into its constituent ions water. Example: Ammonia. Similarly, weak acids do not dissociate into its constituent ions when dissolved in water. Example: Acetic acid.