R
The doublestruck letter R denotes the field of real numbers.
See also
C, N, Q, R--, R-+, R-n, Real Number, ZExplore with Wolfram|Alpha
WolframAlpha
More things to try:
References
Dummit, D. S. and Foote, R. M. "Basics." §0.1 in Abstract Algebra, 3rd ed. Hoboken, NJ: Wiley, p. 1, 2004.Referenced on Wolfram|Alpha
RCite this as:
Weisstein, Eric W. "R." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/R.html