Definition:Dyadic Rational

Definition
A dyadic rational is a rational number whose denominator, when expressed in canonical form, is an integral power of $2$.

That is, $a \in \Q$ is dyadic :
 * $\exists p \in \Z, q \in \Z_{>0}: a = \dfrac p {2^q}$

Also see

 * Definition:P-adic Number, of which this is an instance