radius
Radius (noun) means a straight line from the center of a circle or sphere to its edge, or the length of that line. Example: “The radius of the circle is exactly five centimeters.”
How to use radius
Learner’s notesIn plain EnglishThe distance from the center of a circle to its edge, or (loosely) the surrounding area within a given distance; also a bone in the forearm.
Word forms
radiused past tense, radii plural, radiuses plural, radiuses singular
Fill the gap
Can you complete this real example?
The _____ of the circle is exactly five centimeters.
Etymology
Borrowed directly from Latin radius, meaning "ray" or "spoke".
Synonyms
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Rhymes for radius
See all rhymes for radius →Frequently asked questions
What does “radius” mean?
The word “radius” means a straight line from the center of a circle or sphere to its edge, or the length of that line. In plain terms, the distance from the center of a circle to its edge, or (loosely) the surrounding area within a given distance; also a bone in the forearm.
How do you pronounce “radius”?
“Radius” is pronounced RAY-dee-uhs (/ˈɹeɪ.di.əs/ in IPA).
How do you use “radius” in a sentence?
Here is “radius” used in a sentence: “The radius of the circle is exactly five centimeters.”
What part of speech is “radius”?
“Radius” is a noun.
Where does the word “radius” come from?
The word “radius” comes from Latin. Borrowed directly from Latin radius, meaning "ray" or "spoke".
Is “radius” a common word?
“Radius” is a fairly common word in modern English.
How many meanings does “radius” have?
“Radius” has 3 distinct senses listed in this dictionary. The most common is: a straight line from the center of a circle or sphere to its edge, or the length of that line.
What is the difference between radius and diameter?
The radius is the straight line from the center of a circle to its edge, while the diameter is a line that passes through the center and connects two opposite points on the edge. The diameter is always exactly twice the length of the radius.
What does radius mean in a phrase like 'within a five-mile radius'?
In this usage, radius refers to a surrounding area or distance measured outward from a central point, such as a location or event. 'Within a five-mile radius' means anywhere inside a circle extending five miles from that point.
Where is the radius bone located in the body?
The radius is the long bone of the forearm on the thumb side, running from the elbow to the wrist. It works alongside the ulna, the other forearm bone, to allow rotation of the hand.