SKIP TO CONTENT

r

Definitions of r
  1. noun
    the 18th letter of the Roman alphabet
    synonyms: R
    see moresee less
    type of:
    alphabetic character, letter, letter of the alphabet
    the conventional characters of the alphabet used to represent speech
  2. noun
    the length of a line segment between the center and circumference of a circle or sphere
    synonyms: radius
    see moresee less
    types:
    semidiameter
    the apparent radius of a celestial body when viewed as a disc from the earth
    radius of curvature
    the radius of the circle of curvature; the absolute value of the reciprocal of the curvature of a curve at a given point
    type of:
    length
    the linear extent in space from one end to the other; the longest dimension of something that is fixed in place
Word Family
EDITOR’S CHOICE

Test prep from the experts

Boost your test score with programs developed by Vocabulary.com’s experts.

  • Proven methods: Learn faster, remember longer with our scientific approach.
  • Personalized plan: We customize your experience to maximize your learning.
  • Strategic studying: Focus on the words that are most crucial for success.

SAT/PSAT

$29.95
  • Number of words: 500+
  • Duration: 8 weeks or less
  • Time: 1 hour / week

TOEFL

$29.95
  • Number of words: 500+
  • Duration: 10 weeks or less
  • Time: 1 hour / week

ACT

$29.95
  • Number of words: 700+
  • Duration: 10 weeks
  • Time: 1 hour / week