固有频率（Natural frequency）
系统的动能恰好等于其势能时所对应的频率。对于机械系统，它对应于系统的惯性力恰好被弹簧回复力所平衡的频率；对于电气系统，它对应于系统的感抗恰好被容抗所平衡的频率。
大多数机械系统都有许多个固有频率。如果一个机械系统（例如谐振器）发生变形后被释放，它将以其固有频率的某种组合进行振动。
另请参阅谐振。
Natural frequency
A frequency at which the system's kinetic energy exactly equals its potential energy. For a mechanical system, this corresponds to a frequency at which the system's inertial force is exactly balanced by the restoring spring force. For an electrical system, this corresponds to a frequency at which the system's inductive impedance is exactly balanced by its capacitive impedance.
Most mechanical systems have many natural frequencies. If a mechanical system (such as a resonator) is deformed and the released, it will vibrate with some combination of its natural frequencies.
Also see resonance.