- published: 08 Oct 2009
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A circle is a simple shape of Euclidean geometry consisting of those points in a plane that are equidistant from a given point, the centre. The distance between any of the points and the centre is called the radius.
Circles are simple closed curves which divide the plane into two regions: an interior and an exterior. In everyday use, the term "circle" may be used interchangeably to refer to either the boundary of the figure, or to the whole figure including its interior; in strict technical usage, the circle is the former and the latter is called a disk.
A circle can be defined as the curve traced out by a point that moves so that its distance from a given point is constant.
A circle may also be defined as a special ellipse in which the two foci are coincident and the eccentricity is 0. Circles are conic sections attained when a right circular cone is intersected by a plane perpendicular to the axis of the cone.
A circle's diameter is the length of a line segment whose endpoints lie on the circle and which passes through the centre. This is the largest distance between any two points on the circle. The diameter of a circle is twice the radius, or distance from the centre to the circle's boundary. The terms "diameter" and "radius" also refer to the line segments which fit these descriptions. The circumference is the distance around the outside of a circle.
Friendship is a relationship between two people who hold mutual affection for each other. Friendships and acquaintanceship are thought of as spanning across the same continuum. The study of friendship is included in the fields of sociology, social psychology, anthropology, philosophy, and zoology. Various academic theories of friendship have been proposed, including social exchange theory, equity theory, relational dialectics, and attachment styles.
The value of friendship is often the result of friends consistently demonstrating the following:
Friendship was a topic of moral philosophy which was greatly discussed by Plato, Aristotle, and the Stoics. This was less discussed in the modern era, until the re-emergence of contextualist and feminist approaches to ethics. Openness in friendship was seen as an enlargement of the self; Aristotle wrote, "The excellent person is related to his friend in the same way as he is related to himself, since a friend is another self; and therefore, just as his own being is choiceworthy him, the friend's being is choice-worthy for him in the same or a similar way." In Ancient Greek, the same word was used for "friend" and "lover".
Unknown or The Unknown may refer to: