Simplicity is the state or quality of being simple. It usually relates to the burden which a thing puts on someone trying to explain or understand it. Something which is easy to understand or explain is simple, in contrast to something complicated. Alternatively, as Herbert A. Simon suggested, something is simple or complex depending on the way we choose to describe it.

In some uses, simplicity can be used to imply beauty, purity, or clarity. Simplicity may also be used in a negative connotation to denote a deficit or insufficiency of nuance or complexity of a thing, relative to what is supposed to be required.

The concept of simplicity has been related to truth in the field of epistemology. According to Occam's razor, all other things being equal, the simplest theory is the most likely to be true. In the context of human lifestyle, simplicity can denote freedom from hardship, effort or confusion. Specifically, it can refer to a simple living lifestyle.

Simplicity is a theme in the Christian religion. According to St. Thomas Aquinas, God is infinitely simple. The Roman Catholic and Anglican religious orders of Franciscans also strive after simplicity. Members of the Religious Society of Friends (Quakers) practice the Testimony of Simplicity, which is the simplifying of one's life in order to focus on things that are most important and disregard or avoid things that are least important.

In the philosophy of science, simplicity is a meta-scientific criterion by which to evaluate competing theories. In this field, a distinction is often made between two senses of simplicity: syntactic simplicity (the number and complexity of hypotheses), and ontological simplicity (the number and complexity of things postulated). These two aspects of simplicity are often referred to as elegance and parsimony respectively.

Famous quotes containing the word simplicity:

    The Americans never use the word peasant, because they have no idea of the class which that term denotes; the ignorance of more remote ages, the simplicity of rural life, and the rusticity of the villager have not been preserved among them; and they are alike unacquainted with the virtues, the vices, the coarse habits, and the simple graces of an early stage of civilization.
    Alexis de Tocqueville (1805–1859)

    Every New Englander might easily raise all his own breadstuffs in this land of rye and Indian corn, and not depend on distant and fluctuating markets for them. Yet so far are we from simplicity and independence that, in Concord, fresh and sweet meal is rarely sold in the shops, and hominy and corn in a still coarser form are hardly used by any.
    Henry David Thoreau (1817–1862)