Planetary/epicyclic gears without gyroscopic effects yield real-valued modes that are categorized into mode types. These mode types, however, do not make full use of the highly structured modal properties. This work shows that the mode types, and each mode type’s corresponding mode properties, can be better utilized by constructing complex-valued modes from the real-valued modes that arise from non-gyroscopic planetary gear models. The benefits of complex-valued modes are evident from gyroscopic spinning system models, where complex-valued modes are unavoidable. For planetary gears with rigid-body central components (i.e., carrier, ring gear, and sun gear) having six lumped-parameter degrees of freedom, these real-valued modes are usually categorized into three types: rotational-axial, translational-tilting, and planet modes. Similar categorizations occur for in-plane (i.e., spur gear) and purely rotational degree of freedom models. For planetary gears with one or more elastic central components, the real-valued modes are categorized into \(\text {int}(N/2) +1\) types, where N is the number of planets. None of these mode categorizations make full use of the modal properties. To make the mode categorization more valuable, we transform real-valued modes to complex-valued modes of N types. A finer mode categorization with \(N> \text {int}(N/2) +1\) mode types yields finer mode participation, resonance suppression, and parametric instability suppression rules that arise from cyclic symmetry and mesh phasing. These rules are crucial for vibration reduction and experimental analysis of planetary gears. A physical interpretation of the complex-valued modes illustrates how they can be used in dynamics.