Wisdom is a deep understanding and realization of people, things, events or situations, resulting in the ability to apply perceptions, judgements and actions in keeping with this understanding. It often requires control of one's emotional reactions (the "passions") so that universal principles, reason and knowledge prevail to determine one's actions. Wisdom is also the comprehension of what is true coupled with optimum judgment as to action. Synonyms include: sagacity, discernment, or insight.

A basic definition of wisdom is to make the best use of knowledge. The opposite of wisdom is folly.

Dr. Kleinman suggests that by mentoring and caring for others, one comes closer to fulfilling the search for wisdom.

The ancient Greeks considered wisdom to be an important virtue, personified as the goddesses Metis and Athena. Athena is said to have sprung from the head of Zeus. She was portrayed as strong, fair, merciful, and chaste. To Socrates and Plato, philosophy was literally the love of Wisdom (philo-sophia). This permeates Plato's dialogues, especially The Republic, in which the leaders of his proposed utopia are to be philosopher kings: rulers who understand the Form of the Good and possess the courage to act accordingly. Aristotle, in his Metaphysics, defined wisdom as the understanding of causes, i.e. knowing why things are a certain way, which is deeper than merely knowing that things are a certain way.