radius

/ˈɹeɪ.di.əs/

//ˈɹeɪ.di.əs// noun

By · According to Wiktionary data (CC BY-SA) ·

"radius" is a 6-letter English headword indexed on PlainSpell.

The verdict

“radius” is a regularly-used English word, ranked #8,847 in English word frequency and used as a noun.

#8,847
frequency rank, English
6
letters
8
tracked misspellings
7
confusable pairs

According to Wiktionary data (CC BY-SA, analyzed May 6, 2026) - The long bone in the forearm, on the side of the thumb.

Visual similarity to commonly confused words

How many letter changes separate each confused pair (Levenshtein distance, normalized).

radius vs rains
67% similar
radius vs rails
67% similar
radius vs radio
67% similar

Source: PlainSpell confusable corpus (Wiktionary, CC BY-SA).

Key facts for radius
PropertyValue
Headwordradius
LanguageEnglish
Part of speechNoun
IPA/ˈɹeɪ.di.əs/
Letters6
Frequency rank#8,847
Misspellings tracked8
Confusable pairs7
SourceWiktionary (kaikki.org)

Where “radius” sits in English frequency

Every-word frequency runs from the handful of words we use constantly (left) to the long tail used once in a blue moon (right). radius lands here:

#1#100#1K#10K#100K
← used constantlyrarely used →

Scale is logarithmic (each tick is 10× rarer). Source: FrequencyWords open word-frequency list.

Spelling & Dictionary Insight

The English entry for radius is 6 letters long, classified as a noun, and transcribed in the International Phonetic Alphabet as /ˈɹeɪ.di.əs/. Corpus data places it at rank #8,847 in overall English word frequency, indicating it appears regularly in written and spoken text. Wiktionary records 7 distinct senses for this headword, so context determines which meaning a reader should apply.

Our generated misspelling index lists 8 likely wrong-spelling variants for radius, with forms such as "ardius", "raddius", and "radisu". Every one of these variants traces to a single-character edit -- an added or dropped letter, a swapped consonant, or a vowel swap -- the kind of slip a spell-checker is built to catch. It also participates in 7 confusable-pair relationships, "rains", "rails", "radio", and more, where similar look or sound leads writers to substitute one word for another in context.

Etymologically, the entry records: Borrowed from Latin radius (“ray”). Doublet of ray. The correct English form is radius, spelled R-A-D-I-U-S.

Definition

  1. 1
    The long bone in the forearm, on the side of the thumb.
  2. 2
    The lighter bone (or fused portion of bone) in the forelimb of an animal.
  3. 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. 4
    A line segment between any point of a circle or sphere and its center.
  5. 5
    The length of this line segment.
  6. 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. 7
    The minimum eccentricity of any vertex, for a given graph.

Etymology

Borrowed from Latin radius (“ray”). Doublet of ray.

Synonyms

R

This word in other languages

radio(Español)radius(Français)Speiche(Deutsch)rádio(Português)

Common misspellings

Also misspelled as: ardius,raddius,radisu,radiuss,raduis,raidus,rdaius,rradius

Misspelling Pattern Breakdown

How far each generated variant is from the correct spelling of radius - measured in single-character edits (insert, delete, or substitute a letter). Larger bars are easier to catch; one-edit slips are the sneakiest.

ardius2raddius1radisu2radiuss1raduis2raidus2rdaius2rradius1
Edit distance from "radius"

Definitions, pronunciation, and etymology for this entry are drawn from Wiktionary via the kaikki.org structured extract (CC BY-SA); frequency ordering uses the FrequencyWords open word-frequency list (2018 English corpus, MIT). See the methodology for how each field is sourced and updated.

Frequently Asked Questions

How do you spell "radius"?
"radius" is spelled R-A-D-I-U-S. The IPA pronunciation is /ˈɹeɪ.di.əs/.
What does "radius" mean?
As a noun, "radius" means: The long bone in the forearm, on the side of the thumb.
What words are commonly confused with "radius"?
"radius" is commonly confused with "rains", "rails", "radio". These words look or sound similar but have different meanings. PlainSpell provides detailed comparisons for each pair.
How do you pronounce "radius"?
The IPA (International Phonetic Alphabet) transcription for "radius" is /ˈɹeɪ.di.əs/. Click the speaker icon on the pronunciation badge above to hear it spoken aloud where audio is available.
What is the origin of the word "radius"?
Borrowed from Latin radius (“ray”). Doublet of ray. See the full etymology section above for more details.
Is PlainSpell free to use?
Yes, PlainSpell is a completely free word reference. You can look up definitions, pronunciations, confusable pairs, homophones, and spelling corrections across 5 languages without any sign-up or subscription.

Using “radius”

The practical upshot for anyone who landed here from a spell-check.

  • The one correct English spelling is R-A-D-I-U-S - every other letter order is a misspelling in standard orthography.
  • Say it as /ˈɹeɪ.di.əs/ (IPA); tap the speaker on the pronunciation badge to hear it where audio exists.
  • Don't mix it up with “rains” - see the side-by-side comparison. radius vs rains
  • Browse more English words and confusable pairs in the same reference. English words
Data Source

Wiktionary (via kaikki.org), licensed under CC BY-SA & GFDL. Word ordering uses an open word-frequency list; misspelling variants are generated by edit-distance from the correct headword.

Source: Wiktionary (via kaikki.org) Structured Wiktionary extract

Source: FrequencyWords open word-frequency list FrequencyWords open word-frequency list