R
| Pronunciation (US): |   |
Dictionary entry overview: What does R mean?
• R (noun)
The noun R has 4 senses:
1. a unit of radiation exposure; the dose of ionizing radiation that will produce 1 electrostatic unit of electricity in 1 cc of dry air
2. (physics) the universal constant in the gas equation: pressure times volume = R times temperature; equal to 8.3143 joules per kelvin per mole
3. the 18th letter of the Roman alphabet
4. the length of a line segment between the center and circumference of a circle or sphere
Familiarity information: R used as a noun is uncommon.
Dictionary entry details
• R (noun)
Meaning:
A unit of radiation exposure; the dose of ionizing radiation that will produce 1 electrostatic unit of electricity in 1 cc of dry air
Classified under:
Nouns denoting quantities and units of measure
Synonyms:
R; roentgen
Hypernyms ("R" is a kind of...):
radioactivity unit (a measure of radioactivity)
Meaning:
(physics) the universal constant in the gas equation: pressure times volume = R times temperature; equal to 8.3143 joules per kelvin per mole
Classified under:
Nouns denoting quantities and units of measure
Synonyms:
gas constant; universal gas constant; R
Hypernyms ("R" is a kind of...):
constant (a number representing a quantity assumed to have a fixed value in a specified mathematical context)
Domain category:
natural philosophy; physical science; physics (the science of matter and energy and their interactions)
Meaning:
The 18th letter of the Roman alphabet
Classified under:
Nouns denoting communicative processes and contents
Synonyms:
letter r; R
Hypernyms ("R" is a kind of...):
alphabetic character; letter; letter of the alphabet (the conventional characters of the alphabet used to represent speech)
Holonyms ("R" is a member of...):
Latin alphabet; Roman alphabet (the alphabet evolved by the ancient Romans which serves for writing most of the languages of western Europe)
Meaning:
The length of a line segment between the center and circumference of a circle or sphere
Classified under:
Nouns denoting attributes of people and objects
Synonyms:
radius; r
Hypernyms ("r" is a kind of...):
length (the linear extent in space from one end to the other; the longest horizontal dimension of something that is fixed in place)
Hyponyms (each of the following is a kind of "r"):
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)
Holonyms ("r" is a part of...):
diam; diameter (the length of a straight line passing through the center of a circle and connecting two points on the circumference)
