radius
ra·di·us/ˈɹeɪ.di.əs/noun, verb
radius is spelled R-A-D-I-U-S: 6 letters and 3 syllables (ra·di·us). It appears 7.2 times per million words in written English, the 8,784th most frequent word form (wordfreq, 2021 data). As a noun, radius means “The long bone in the forearm, on the side of the thumb” (English Wiktionary, September 2026). The plural of radius is radii or radiuses.
How many letters and syllables are in radius?
| Letters | 6: R-A-D-I-U-S |
|---|---|
| Syllables | 3: ra·di·us |
| In writing | 7.2 times per million words; the 8,784th most frequent word form |
| Wrong spellings searched | none measured in search |
Sources: letters and syllables from the English Wiktionary's hyphenation or pronunciation; written frequency: wordfreq 3.1 (a 2021 snapshot of Wikipedia, subtitles, news, books, web text and social media).
How common is radius?
Radius appears 7.2 times per million words in written English, the 8,784th most frequent word form in the list.
Source: written frequency: wordfreq 3.1 (a 2021 snapshot of Wikipedia, subtitles, news, books, web text and social media).
How do you pronounce radius?
- /ˈɹeɪ.di.əs/
Radius has 3 syllables, split ra·di·us in writing.
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract). Recordings: En-us-radius.ogg, Wikimedia Commons (author and licence on each file's page).
Forms of radius
- radii plural
- radiuses plural, present, singular, he/she/it
- radiusing participle, present
- radiused participle, past
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract).
What does radius mean?
The meanings the English Wiktionary records, quoted as written there (source below).
noun
- 1
The long bone in the forearm, on the side of the thumb.
- 2
The lighter bone (or fused portion of bone) in the forelimb of an animal.
- 3
One of the major veins of the insect wing, between the subcosta and the media; the vein running along the costal edge of the discal cell.
- 4
A line segment between any point of a circle or sphere and its center.
Fatima claims to have visited all the bars within a five-mile radius of her Manhattan apartment.
- 5
The length of this line segment.
- 6
Anything resembling a radius, such as the spoke of a wheel, the movable arm of a sextant, or one of the radiating lines of a spider's web.
- 7
The minimum eccentricity of any vertex, for a given graph.
verb
- 1
To give a rounded edge to.
noun
- 1
Initialism of Remote Authentication Dial-In User Service.
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract).
Radius in Spanish, French, German and Portuguese
| Language | Words |
|---|---|
| French | radius , rayon |
| German | Speiche, Radius , Halbmesser |
| Portuguese | rádio , raio |
| Spanish | radio |
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract). Translations are Wiktionary's, by sense; a linked word has its own PlainSpell page.
Where does radius come from?
Borrowed from Latin radius (“ray”). Doublet of ray.
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract).