Definition of "radius" []

• Mathematics A line segment that joins the center of a circle with any point on its circumference. (noun)
• Mathematics A line segment that joins the center of a sphere with any point on its surface. (noun)
• Mathematics A line segment that joins the center of a regular polygon with any of its vertices. (noun)
• Mathematics The length of any such line segment. (noun)
• A circular area measured by a given radius: every family within a radius of 25 miles of the city center. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "The radius, _p b_, of the upper circle is termed the _crater radius_; the line _o p_, drawn from the centre of the charge perpendicular to the surface where the explosion takes place, is termed the _line of least resistance_; the line _o b_, drawn from the centre of the powder to any point in the circumference of the upper circle, is termed the _radius of explosion_."
• "Not to mention I live near Philadelphia, PA and he will not shoot outside of a certain radius away from the city, which would mean filming of BD would be nearby."
• "Indeed, Mars's satellite Phobos, whose mean radius is 11.1 km, has a numerically similar escape velocity of 11.3 metres per second - as you may vaguely remember fron Arthur C. Clarke's story, "Hide-and-Seek"."