The fundamental dielectric properties of nematic liquid crystals were measured in the 3-33 GHz frequency range for the purpose of applying liquid crystals to adaptive devices in the microwave and millimeter-wave ranges. We proposed two kinds of measurement methods. Firstly, we used the cut back method to determine the NLCs' permittivity and loss tangent, which is the first time it has been used for this purpose. Secondly, the dielectric permittivity of nematic liquid crystals used for the microstrip-line devices were determined in the 3-33 GHz frequency range by using a newly developed inductive coupled ring resonator. In addition, the effective alignment coefficient eta(alpha)(eta(alpha) < 1) is proposed for the determination of the effective epsilon'(parallel to) (the long axis of the liquid crystal molecules is parallel to the direction of the r.f. electric field E-rf) because the value of epsilon'(parallel to) must be modified to eta(alpha)epsilon'(parallel to) in the microstrip-line structure. This concept is useful for the design of the microstrip-line-type variable delay lines.