Real-linear map
= Real-linear map
{title2=$f(rx)=rf(x)\quad(r\in\mathbb R)$}
A <real-linear map> is a <linear map> over the <real numbers>. For a map from the <real line> to itself, real linearity means <multiplication> by a fixed <real number>, its value at one. <Rational-linear maps> need not be real-linear without an additional regularity condition.