In electric devices You can change the size of resonator by using lumped components. For example in wire antennas if You add inductor, the electricel lenght will be bigger. According to it You can make antenna shorter physically but the electrical lenght is the half of wavelenght.
Also it depends of the material Your are using to build resonator. For example in dielectric resonators, wavelenght in dielectric material is shorter then in free space. So, You can achive smaller dimensions of resonator. It depends on dielectric permability. There is a lot of possiblities.
The conditions I've mentioned are generall. There are of course lot of other ways to achive resonans.