A Bode plot represents the frequency response of a continuous-time system using a logarithmic frequency axis.

The magnitude is commonly expressed in decibels:

$$20\log_{10}|H(i\omega)|,$$

while the phase plot shows

$$\arg H(i\omega)$$

as a function of frequency.

The logarithmic axis makes many decades of frequency visible at once and turns multiplicative gains into additive vertical shifts. Products of transfer-function factors also become sums of their decibel contributions.

A factor that changes behavior around a characteristic frequency produces a corresponding change in magnitude slope and phase. This makes poles and zeros visually identifiable once their effects are understood.

Bode plots summarize both how strongly a system responds at each frequency and how much phase shift it introduces. They are widely used for filters, physical dynamics and feedback systems.