r

1. recto.
2. (giving position or direction) right.

   l to r: Evan, Nic, and David

3. rule.

   under r 7.4 (6) the court may hear an application immediately

1. radius.

   2πr

2. correlation coefficient.

   sigmoidoscopic and symptom scores also showed a significant correlation with each other (r = 0.91)

noun

the eighteenth letter of the alphabet.

1. rand.

   a farm worth nearly R1,3 million

2. (in names of sports clubs) Rangers or Rovers.

   Berwick R

   Featherstone R

3. Réaumur (a temperature scale, now obsolete).

   198.6 °R

4. Regina or Rex.

   Elizabeth R

5. registered as a trademark.
6. (in the US) Republican.
7. (in film classification) restricted (denoting films restricted to viewers over a certain age).
8. (on a gear shift) reverse.
9. River (chiefly on maps).
10. roentgen(s).
11. Romania (international vehicle registration).
12. rook (in recording moves in chess).

    21.Rh4

13. (on scorecards) run(s).

1. an unspecified alkyl or other organic radical or group.
2. electrical resistance.
3. the gas constant.

noun, symbol

a number between +1 and −1 calculated so as to represent the linear interdependence of two variables or sets of data.

noun, symbol

the constant of proportionality in the gas equation. It is equal to 8.314 joule kelvin⁻¹ mole⁻¹.

noun, symbol

a unit of ionizing radiation, the amount producing one electrostatic unit of positive or negative ionic charge in one cubic centimetre of air under standard conditions.

1920s: named after Wilhelm Conrad Röntgen (1845–1923), German physicist, discoverer of X-rays.