**Definition:**In signal processing, filter order refers to the number of poles (or zeros) in the transfer function of a filter. Poles and zeros are locations in the complex plane where the transfer function becomes infinite or zero, respectively. The order of a filter is equal to the number of poles or zeros, whichever is greater.In general, the filter order can be determined by counting the number of poles (or zeros) in the transfer function, or by finding the highest power of the variable in the transfer function.

**Alternative definition:**The order of the filter refers to the maximum delay in samples used in generating each output sample. The higher the order the steeper the slope between passband and stopband.

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**Related terms:**Filter, FIR FIlter, IIR Filter, Preprocessing